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{{Infobox niobium}}

'''Niobium''' is a [[chemical element]]; it has [[chemical symbol|symbol]] '''Nb''' (formerly '''columbium''', '''Cb''') and [[atomic number]] 41. It is a light grey, crystalline, and [[Ductility|ductile]] [[transition metal]]. Pure niobium has a [[Mohs scale of mineral hardness|Mohs hardness]] rating similar to pure [[titanium]],<ref name="r1">{{cite book |editor=G.V. Samsonov |chapter=Mechanical Properties of the Elements |doi=10.1007/978-1-4684-6066-7_7 |isbn=978-1-4684-6066-7 |pages=387–446 |publisher=IFI-Plenum |place=New York, US |year=1968 |last1=Samsonov |first1=G. V. |title=Handbook of the Physicochemical Properties of the Elements }}</ref> and it has similar ductility to [[iron]]. Niobium oxidizes in Earth's atmosphere very slowly, hence its application in jewelry as a [[hypoallergenic]] alternative to [[nickel]]. Niobium is often found in the minerals [[pyrochlore]] and [[columbite]]. Its name comes from Greek mythology: [[Niobe]], daughter of [[Tantalus]], the namesake of [[tantalum]]. The name reflects the great similarity between the two elements in their physical and chemical properties, which makes them difficult to distinguish.<ref>{{cite book |last1=Knapp |first1=Brian |title=Francium to Polonium |date=2002 |publisher=Atlantic Europe Publishing Company |isbn=0-7172-5677-4 |page=40}}</ref>

English chemist [[Charles Hatchett]] reported a new element similar to tantalum in 1801 and named it columbium. In 1809, English chemist [[William Hyde Wollaston]] wrongly concluded that tantalum and columbium were identical. German chemist [[Heinrich Rose]] determined in 1846 that tantalum ores contain a second element, which he named niobium. In 1864 and 1865, a series of scientific findings clarified that niobium and columbium were the same element (as distinguished from tantalum), and for a century both names were used interchangeably. Niobium was officially adopted as the name of the element in 1949, but the name columbium remains in current use in metallurgy in the United States.
	
It was not until the early 20th century that niobium was first used commercially. Niobium is an important addition to high-strength low-alloy steels. Brazil is the leading producer of niobium and [[ferroniobium]], an alloy of 60–70% niobium with iron. Niobium is used mostly in alloys, the largest part in special steel such as that used in gas pipelines. Although these alloys contain a maximum of 0.1%, the small percentage of niobium enhances the strength of the steel by scavenging [[carbide]] and [[nitride]]. The temperature stability of niobium-containing [[superalloy]]s is important for its use in jet and rocket engines.

Niobium is used in various [[Superconductivity|superconducting]] materials. These alloys, also containing titanium and tin, are widely used in the superconducting magnets of [[Magnetic resonance imaging|MRI scanners]]. Other applications of niobium include welding, nuclear industries, electronics, optics, and jewelry. In the last application, the low toxicity and iridescence produced by [[anodization]] are highly desired properties.{{cn|date=September 2025}}

==History==
[[File:Charles Hatchett. Soft-ground etching by F. C. Lewis after T Wellcome V0002614 (cropped).jpg|thumb|left|English chemist [[Charles Hatchett]] identified the element ''columbium'' in 1801 within a mineral discovered in Connecticut, US.|alt=Oval black and white painting of a man with a prominent shirt collar and necktie]]
[[File:Sommer, Giorgio (1834-1914) - n. 2990 - Niobe madre - Firenze.jpg|left|thumb|upright=0.5|Picture of a Hellenistic sculpture representing ''Niobe'' by [[Giorgio Sommer]]|alt=Black and white image of a marmor sculpture of a bowing woman with a child nestling in her lap]]

Niobium was identified by English chemist Charles Hatchett in 1801.<ref name="Hatchett_1802a">{{cite journal|last=Hatchett|first=Charles|author-link=Charles Hatchett|year=1802|url=https://books.google.com/books?id=c-Q_AAAAYAAJ&pg=PA49|title=An analysis of a mineral substance from North America, containing a metal hitherto unknown|journal=Philosophical Transactions of the Royal Society of London|volume=92|pages=49–66|jstor=107114|doi=10.1098/rspl.1800.0045|doi-access=free|access-date=15 July 2016|archive-date=3 May 2016|archive-url=https://web.archive.org/web/20160503233004/https://books.google.com/books?id=c-Q_AAAAYAAJ&pg=PA49|url-status=live|url-access=subscription}}</ref><ref name="Hatchett_1802b">{{Citation |last=Hatchett |first=Charles |author-link=Charles Hatchett |year=1802 |title=Outline of the Properties and Habitudes of the Metallic Substance, lately discovered by Charles Hatchett, Esq. and by him denominated Columbium |journal=[[Journal of Natural Philosophy, Chemistry, and the Arts]] |volume=I (January) |pages=32–34 |url=https://books.google.com/books?id=ylZwOmyBA7IC&pg=PA32 |postscript=. |access-date=13 July 2017 |archive-date=24 December 2019 |archive-url=https://web.archive.org/web/20191224164852/https://books.google.com/books?id=ylZwOmyBA7IC&pg=PA32 |url-status=live }}</ref><ref name="Hatchett_1802c">{{cite journal |last=Hatchett |first=Charles |author-link=Charles Hatchett |year=1802 |title=Eigenschaften und chemisches Verhalten des von Charles Hatchett entdeckten neuen Metalls, Columbium |trans-title=Properties and chemical behavior of the new metal, columbium, (that was) discovered by Charles Hatchett |language=de |journal=[[Annalen der Physik]] |volume=11 |issue=5 |pages=120–122 |url=https://books.google.com/books?id=wSYwAAAAYAAJ&pg=PA120 |doi=10.1002/andp.18020110507 |bibcode=1802AnP....11..120H |access-date=15 July 2016 |archive-date=9 May 2016 |archive-url=https://web.archive.org/web/20160509100435/https://books.google.com/books?id=wSYwAAAAYAAJ&pg=PA120 |url-status=live }}</ref> He found a new element in a mineral sample that had been sent to England from Connecticut, United States in 1734 by John Winthrop [[Fellow of the Royal Society|FRS]] (grandson of [[John Winthrop the Younger]]) and named the mineral "columbite"" and the new element "columbium" after ''[[Columbia (name)|Columbia]]'', the poetic name for the United States.<ref name="Noyes" /><ref name="1853 Mining Journal">{{cite journal|last=Percival|first=James|title=Middletown Silver and Lead Mines|journal=Journal of Silver and Lead Mining Operations|date=January 1853|volume=1|page=186|url=https://play.google.com/store/books/details?id=MFILAAAAYAAJ&rdid=book-MFILAAAAYAAJ&rdot=1|access-date=24 April 2013|archive-date=3 June 2013|archive-url=https://web.archive.org/web/20130603002528/https://play.google.com/store/books/details?id=MFILAAAAYAAJ&rdid=book-MFILAAAAYAAJ&rdot=1|url-status=live}}</ref><ref>{{cite journal|title = Charles Hatchett FRS (1765–1847), Chemist and Discoverer of Niobium|first = William P.|last = Griffith|author2=Morris, Peter J. T. |journal = Notes and Records of the Royal Society of London|volume = 57|issue = 3|pages = 299–316|date = 2003|jstor = 3557720|doi = 10.1098/rsnr.2003.0216|s2cid = 144857368}}</ref> The ''columbium'' discovered by Hatchett was probably a mixture of the new element with tantalum.<ref name="Noyes">{{cite book| last = Noyes| first = William Albert| title = A Textbook of Chemistry| publisher = H. Holt & Co.| page = 523| url = https://books.google.com/books?id=UupHAAAAIAAJ&q=columbium+discovered+by+Hatchett+was+a+mixture+of+two+elements&pg=PA523| date = 1918| access-date = 2 November 2020| archive-date = 2 June 2022| archive-url = https://web.archive.org/web/20220602091834/https://books.google.com/books?id=UupHAAAAIAAJ&q=columbium+discovered+by+Hatchett+was+a+mixture+of+two+elements&pg=PA523| url-status = live}}</ref>

Subsequently, there was considerable confusion<ref name="Wolla">{{cite journal|title = On the Identity of Columbium and Tantalum|pages = 246–252|journal = Philosophical Transactions of the Royal Society|first = William Hyde|last = Wollaston|author-link = William Hyde Wollaston|doi = 10.1098/rstl.1809.0017| jstor = 107264|volume = 99|date = 1809|s2cid = 110567235}}</ref> over the difference between columbium (niobium) and the closely related tantalum. In 1809, English chemist [[William Hyde Wollaston]] compared the oxides derived from both columbium—columbite, with a density 5.918&nbsp;g/cm{{sup|3}}, and tantalum—[[tantalite]], with a density over 8&nbsp;g/cm{{sup|3}}, and concluded that the two oxides, despite the significant difference in density, were identical; thus he kept the name tantalum.<ref name="Wolla" /> This conclusion was disputed in 1846 by German chemist [[Heinrich Rose]], who argued that there were two different elements in the tantalite sample, and named them after children of Tantalus: ''niobium'' (from Niobe) and ''[[pelopium]]'' (from [[Pelops]]).<ref name="Pelop">{{cite journal|title = Ueber die Zusammensetzung der Tantalite und ein im Tantalite von Baiern enthaltenes neues Metall|pages = 317–341|journal = Annalen der Physik|author-link = Heinrich Rose|language = de|first = Heinrich|last = Rose|doi = 10.1002/andp.18441391006|url = http://gallica.bnf.fr/ark:/12148/bpt6k15148n/f327.table|volume = 139|issue = 10|date = 1844|bibcode = 1844AnP...139..317R|access-date = 31 August 2008|archive-date = 20 June 2013|archive-url = https://web.archive.org/web/20130620093605/http://gallica.bnf.fr/ark:/12148/bpt6k15148n/f327.table|url-status = live}}</ref><ref>{{cite journal|title = Ueber die Säure im Columbit von Nordamérika|language = de|pages = 572–577|first = Heinrich|last = Rose|journal = Annalen der Physik|doi = 10.1002/andp.18471460410|url = http://gallica.bnf.fr/ark:/12148/bpt6k15155x/f586.table|date = 1847|volume = 146|issue = 4|author-link = Heinrich Rose|bibcode = 1847AnP...146..572R|access-date = 31 August 2008|archive-date = 11 May 2014|archive-url = https://web.archive.org/web/20140511114909/http://gallica.bnf.fr/ark:/12148/bpt6k15155x/f586.table|url-status = live}}</ref> This confusion arose from the minimal observed differences between tantalum and niobium. The claimed new elements ''pelopium'', ''[[ilmenium]]'', and ''dianium''<ref name="Dianium">{{cite journal|title = Ueber eine eigenthümliche Säure, Diansäure, in der Gruppe der Tantal- und Niob- verbindungen|first = V.|last = Kobell|journal = Journal für Praktische Chemie|volume = 79|issue = 1|pages = 291–303|doi = 10.1002/prac.18600790145|date = 1860|url = https://zenodo.org/record/1427822|access-date = 5 October 2019|archive-date = 5 October 2019|archive-url = https://web.archive.org/web/20191005220552/https://zenodo.org/record/1427822|url-status = live}}</ref> were in fact identical to niobium or mixtures of niobium and tantalum.<ref name="Ilmen" />

The differences between tantalum and niobium were unequivocally demonstrated in 1864 by [[Christian Wilhelm Blomstrand]]<ref name="Ilmen" /> and [[Henri Étienne Sainte-Claire Deville]], as well as [[Louis J. Troost]], who determined the formulas of some of the compounds in 1865<ref name="Ilmen">{{cite journal|title = Tantalsäure, Niobsäure, (Ilmensäure) und Titansäure|journal = Fresenius' Journal of Analytical Chemistry|volume = 5|issue = 1|date = 1866|doi = 10.1007/BF01302537|pages = 384–389|author= Marignac, Blomstrand|author2= Deville, H. |author3= Troost, L. |author4= Hermann, R. |s2cid = 97246260}}</ref><ref name="Gupta" /> and finally by Swiss chemist [[Jean Charles Galissard de Marignac]]<ref>{{cite journal|journal = [[Annales de chimie et de physique]]|title = Recherches sur les combinaisons du niobium|pages = 7–75|author-link = Jean Charles Galissard de Marignac|language = fr|first = M. C.|last = Marignac|url = http://gallica.bnf.fr/ark:/12148/bpt6k34818t/f4.table|date = 1866|volume = 4|issue = 8|access-date = 31 August 2008|archive-date = 5 December 2013|archive-url = https://web.archive.org/web/20131205164055/http://gallica.bnf.fr/ark:/12148/bpt6k34818t/f4.table|url-status = live}}</ref> in 1866, who all proved that there were only two elements. Articles on ''ilmenium'' continued to appear until 1871.<ref>{{cite journal|title = Fortgesetzte Untersuchungen über die Verbindungen von Ilmenium und Niobium, sowie über die Zusammensetzung der Niobmineralien (Further research about the compounds of ilmenium and niobium, as well as the composition of niobium minerals)|first = R.|last = Hermann|journal = Journal für Praktische Chemie|language = de|volume = 3|issue = 1|pages = 373–427|doi = 10.1002/prac.18710030137|date = 1871|url = https://zenodo.org/record/1427850|access-date = 5 October 2019|archive-date = 5 October 2019|archive-url = https://web.archive.org/web/20191005220605/https://zenodo.org/record/1427850|url-status = live}}</ref>

Christian Wilhelm Blomstrand was the first to prepare the metal in 1866, when he [[redox|reduced]] niobium chloride by heating it in an atmosphere of hydrogen.<ref name="nauti">{{cite web|url = http://nautilus.fis.uc.pt/st2.5/scenes-e/elem/e04100.html|title = Niobium|publisher = Universidade de Coimbra|access-date = 5 September 2008|archive-url = https://web.archive.org/web/20071210032159/http://nautilus.fis.uc.pt/st2.5/scenes-e/elem/e04100.html|archive-date = 10 December 2007}}</ref> Although de Marignac was able to produce tantalum-free niobium on a larger scale by 1866, it was not until the early 20th century that niobium was used in incandescent lamp filaments, the first commercial application.<ref name="Gupta" /> This use quickly became obsolete through the replacement of niobium with [[tungsten]], which has a higher melting point. That niobium improves the strength of steel was first discovered in the 1920s, and this application remains its predominant use.<ref name="Gupta" /> In 1961, the American physicist [[Eugene Kunzler]] and coworkers at [[Bell Labs]] discovered that [[niobium–tin]] continues to exhibit superconductivity in the presence of strong electric currents and magnetic fields, making it the first material to support the high currents and fields necessary for useful high-power magnets and electrical power machinery. This discovery enabled—two decades later—the production of long multi-strand cables wound into coils to create large, powerful electromagnets for rotating machinery, particle accelerators, and particle detectors.<ref name="geballe">{{cite journal |last=Geballe |first=Theodore H. |title=Superconductivity: From Physics to Technology |journal=Physics Today |volume=46 |issue=10 |date=October 1993 |pages=52–56 |doi=10.1063/1.881384 |bibcode = 1993PhT....46j..52G }}</ref><ref>{{cite journal |volume=95 |page=1435 |date=1954 |title=Superconductivity of Nb<sub>3</sub>Sn |url=https://archive.org/details/sim_physical-review_1954-09-15_95_6/page/1434 |author=Matthias, B. T. |author2=Geballe, T. H.|author3=Geller, S. |author4=Corenzwit, E. |doi=10.1103/PhysRev.95.1435 |journal=Physical Review |bibcode=1954PhRv...95.1435M |issue=6}}</ref>

===Naming the element===
''Columbium'' (symbol Cb)<ref>{{cite journal|title = Reaction of Tantalum, Columbium and Vanadium with Iodine|first = F.|last = Kòrösy|journal = Journal of the American Chemical Society|date = 1939|volume = 61|issue = 4|pages = 838–843|doi = 10.1021/ja01873a018| bibcode=1939JAChS..61..838K }}</ref> was the name originally given by Hatchett upon his discovery of the metal in 1801.<ref name="Hatchett_1802b" /> The name reflected that the type specimen of the [[ore]] came from the United States of America (Columbia).<ref name="Nicholson_1809">{{Citation |editor-last=Nicholson |editor-first=William |editor-link=William Nicholson (chemist) |year=1809 |title=The British Encyclopedia: Or, Dictionary of Arts and Sciences, Comprising an Accurate and Popular View of the Present Improved State of Human Knowledge |volume=2 |publisher=[[Longman|Longman, Hurst, Rees, and Orme]] |page=284 |url=https://books.google.com/books?id=SzUPAQAAIAAJ&pg=PP284 |postscript=. |access-date=13 July 2017 |archive-date=25 December 2019 |archive-url=https://web.archive.org/web/20191225011934/https://books.google.com/books?id=SzUPAQAAIAAJ&pg=PP284 |url-status=live }}</ref> This name remained in use in American journals—the last paper published by [[American Chemical Society]] with ''columbium'' in its title dates from 1953<ref>{{cite journal|title = Photometric Determination of Columbium, Tungsten, and Tantalum in Stainless Steels|author=Ikenberry, L.|author2=Martin, J. L.|author3=Boyer, W. J.|journal = Analytical Chemistry |date = 1953|volume = 25|issue =9|pages = 1340–1344|doi = 10.1021/ac60081a011 |bibcode=1953AnaCh..25.1340I }}</ref>—while niobium was used in Europe. To end this confusion, the name niobium was chosen for element 41 at the 15th Conference of the Union of Chemistry in Amsterdam in 1949.<ref name="Contro">{{cite journal |first = Geoff|last = Rayner-Canham|author2=Zheng, Zheng |title = Naming elements after scientists: an account of a controversy|journal = Foundations of Chemistry|volume = 10|issue = 1|date = 2008|doi = 10.1007/s10698-007-9042-1|pages = 13–18|s2cid = 96082444}}</ref> A year later this name was officially adopted by the [[International Union of Pure and Applied Chemistry]] (IUPAC) after 100 years of controversy, despite the chronological precedence of the name ''columbium''.<ref name="Contro" /> This was a compromise of sorts;<ref name="Contro" /> the IUPAC accepted tungsten instead of wolfram in deference to North American usage; and niobium instead of ''columbium'' in deference to European usage. While many US chemical societies and government organizations typically use the official IUPAC name, some metallurgists and metal societies still use the original American name, ''columbium''.<ref>{{cite journal|journal = Science|date = 1914|title = Columbium Versus Niobium|pages = 139–140|first = F. W.|last = Clarke|jstor = 1640945|volume = 39|issue = 995|doi = 10.1126/science.39.995.139|pmid = 17780662|bibcode = 1914Sci....39..139C|url = https://zenodo.org/record/1448139|access-date = 5 September 2020|archive-date = 2 June 2022|archive-url = https://web.archive.org/web/20220602091834/https://zenodo.org/record/1448139|url-status = live}}</ref><ref name="patel" /><ref name="Gree">{{cite journal|journal = Catalysis Today|date = 2003|title = Vanadium to dubnium: from confusion through clarity to complexity|pages = 5–11|last = Norman N.|first = Greenwood|doi = 10.1016/S0920-5861(02)00318-8 |volume = 78|issue = 1–4}}</ref><ref>{{cite web| title = ASTM A572 / A572M-18, Standard Specification for High-Strength Low-Alloy Columbium-Vanadium Structural Steel| url = https://www.astm.org/Standards/A572| publisher = ASTM International, West Conshohocken| year = 2018| access-date = 2020-02-12| archive-date = 12 February 2020| archive-url = https://web.archive.org/web/20200212215757/https://www.astm.org/Standards/A572| url-status = live}}</ref>{{overcite|date=September 2025}}

==Characteristics==
===Physical===
Niobium is a lustrous, grey, ductile, [[paramagnetism|paramagnetic]] metal in [[Group 5 element|group 5]] of the periodic table (see table), with an electron configuration in the outermost [[electron shell|shells]] atypical for group 5. Similarly atypical configurations occur in the neighborhood of [[ruthenium]] (44) and [[rhodium]] (45).<ref>{{Cite journal |last=Scerri |first=Eric R. |date=April 2019 |title=Five ideas in chemical education that must die |url=http://link.springer.com/10.1007/s10698-018-09327-y |journal=Foundations of Chemistry |language=en |volume=21 |issue=1 |pages=61–69 |doi=10.1007/s10698-018-09327-y |issn=1386-4238|url-access=subscription }}</ref>

{| class="wikitable"  style="margin:10px; float:right;"
|-
![[Atomic number|Z]] !! Element !! No. of electrons/shell
|-
| 23 || [[vanadium]] || 2, 8, 11, 2
|-
| 41 || niobium || 2, 8, 18, 12, 1
|-
| 73 || tantalum || 2, 8, 18, 32, 11, 2
|-
| 105 || [[dubnium]] || 2, 8, 18, 32, 32, 11, 2
|}

Although it is thought to have a [[body-centered cubic]] crystal structure from absolute zero to its melting point, high-resolution measurements of the thermal expansion along the three crystallographic axes reveal anisotropies which are inconsistent with a cubic structure.<ref>Donohue, J. (1974). ''The Structures of the Elements''. Wiley-Interscience.</ref><ref>{{cite journal |last1=Bollinger |first1=R. K. |last2=White |first2=B. D. |last3=Neumeier |first3=J. J. |last4=Sandim |first4=H. R. Z. |last5=Suzuki |first5=Y. |last6=dos Santos |first6=C. A. M. |last7=Avci |first7=R. |last8=Migliori |first8=A. |last9=Betts |first9=J. B. |date=2011 |title=Observation of a Martensitic Structural Distortion in V, Nb, and Ta |journal=Physical Review Letters |volume=107 |issue=7 |article-number=075503 |doi=10.1103/PhysRevLett.107.075503 |bibcode=2011PhRvL.107g5503B |pmid=21902404|doi-access=free }}</ref> Therefore, further research and discovery in this area is expected.

Niobium becomes a superconductor at [[cryogenics|cryogenic]] temperatures. At atmospheric pressure, it has the highest critical temperature of the elemental superconductors at {{convert|9.2|K|C F}}. Niobium has the greatest [[superconductor#Meissner effect|magnetic penetration depth]] of any element.<ref name="Pein">{{cite journal|title = A Superconducting Nb<sub>3</sub>Sn Coated Multicell Accelerating Cavity|first = M.|last = Peiniger|author2=Piel, H. |journal = IEEE Transactions on Nuclear Science|date= 1985|volume= 32|issue = 5|doi = 10.1109/TNS.1985.4334443|pages = 3610–3612|bibcode = 1985ITNS...32.3610P |s2cid = 23988671}}</ref> In addition, it is one of the three elemental type II superconductors, along with vanadium and [[technetium]]. The superconductive properties are strongly dependent on the purity of the niobium metal.<ref name="Moura">{{cite journal|title=Melting And Purification of Niobium|first=Hernane R.|last = Salles Moura|author2=Louremjo de Moura, Louremjo |journal=AIP Conference Proceedings|volume=927|date=2007|issue=927|pages=165–178|doi=10.1063/1.2770689|bibcode=2007AIPC..927..165M}}</ref>

When very pure, it is comparatively soft and ductile, but impurities make it harder.<ref name="Nowak" />

The metal has a low [[Neutron capture#Capture cross section|neutron capture cross-section]] for thermal neutrons; thus it is used in the nuclear industries where neutron transparent structures are desired.<ref>{{cite journal|title = Columbium Alloys Today|author=Jahnke, L. P.|author2=Frank, R. G.|author3=Redden, T. K.|date = 1960|journal = Metal Progr.|volume = 77|issue = 6|pages = 69–74|osti = 4183692}}</ref><ref>{{cite journal|first = A. V.|last = Nikulina|title = Zirconium-Niobium Alloys for Core Elements of Pressurized Water Reactors|journal = Metal Science and Heat Treatment|volume = 45|issue = 7–8|date = 2003|doi = 10.1023/A:1027388503837|pages = 287–292|bibcode = 2003MSHT...45..287N|s2cid = 134841512}}</ref>

===Chemical===
The metal takes on a bluish tinge when exposed to air at room temperature for extended periods.<ref name="Rubber">{{cite book|title = CRC Handbook of Chemistry and Physics|first = David R.|last = Lide|publisher = CRC Press|date = 2004|isbn = 978-0-8493-0485-9|pages = '''4'''–21|edition = 85th|chapter = The Elements|chapter-url-access = registration|chapter-url = https://archive.org/details/crchandbookofche81lide|url = https://archive.org/details/crchandbookofche81lide|url-access = registration}}</ref> Despite a high melting point in elemental form ({{convert|2468|C|F}}), it is less dense than other [[refractory metals]]. Furthermore, it is corrosion-resistant, exhibits superconductivity properties, and forms [[dielectric]] [[oxide]] layers.{{citation needed|date=September 2025}}

Niobium is slightly less [[electropositive]] and more compact than its predecessor in the periodic table, zirconium, whereas it is virtually identical in size to the heavier tantalum atoms, as a result of the [[lanthanide contraction]].<ref name="Nowak" /> As a result, niobium's chemical properties are very similar to those for tantalum, which appears directly below niobium in the periodic table.<ref name="Gupta">{{cite book|title = Extractive Metallurgy of Niobium|first = C. K.|last = Gupta|author2=Suri, A. K. |publisher = CRC Press|date = 1994 |isbn = 978-0-8493-6071-8|pages = 1–16}}</ref> Although its corrosion resistance is not as outstanding as that of tantalum, the lower price and greater availability make niobium attractive for less demanding applications, such as vat linings in chemical plants.<ref name="Nowak" />

===Isotopes===
{{main|Isotopes of niobium}}
Almost all of the niobium in Earth's crust is the one stable [[isotope]], {{chem2|^{93}Nb}}. The most stable [[radioisotope]] is {{chem2|^{92}Nb}} with [[half-life]] 34.7 million years. {{chem2|^{92}Nb}}, along with the next most stable one, {{chem2|^{94}Nb}} (20,400 years), has been detected in refined samples of terrestrial niobium and may originate from bombardment by [[cosmic ray]] [[muon]]s in Earth's crust.<ref>{{cite journal|last1=Clayton|first1=Donald D.|last2=Morgan|first2=John A.|date=1977|journal=Nature|volume=266|issue=5604|pages=712–713|title=Muon production of <sup>92,94</sup>Nb in the Earth's crust|doi=10.1038/266712a0|s2cid=4292459}}</ref> Isotopes lighter than the stable {{chem2|^{93}Nb}} tend to [[beta decay|β{{sup|+}} decay]], and those that are heavier tend to β{{sup|−}} decay, with some exceptions: β{{sup|+}}-delayed [[proton emission]] is observed for isotopes as heavy as {{chem2|^{84}Nb}}, and {{chem2|^{92}Nb}} alone can decay by both [[positron|β{{sup|+}}]] and [[electron|β{{sup|−}}]] modes.{{cn|date=September 2025}}

The most stable of isomeric state of a niobium isotope is {{chem2|^{93m}Nb}} with half-life {{val|16.12|u=years}}. The long-lived fission product {{chem2|^{93}Zr}} decays, mainly through this isomer, to stable niobium.{{cn|date=September 2025}}

===Occurrence===
{{see also|Category:Niobium minerals}}
Niobium is estimated to be the [[Abundance of elements in Earth's crust|33rd most abundant element in the Earth's crust]], at {{val|20|u=[[parts per million|ppm]]}}.<ref>{{cite book|title = Nature's Building Blocks: An A-Z Guide to the Elements|last = Emsley|first = John|publisher = Oxford University Press|date = 2001|location = Oxford, England|isbn = 978-0-19-850340-8|chapter = Niobium|pages = [https://archive.org/details/naturesbuildingb0000emsl/page/283 283–286]|chapter-url = https://archive.org/details/naturesbuildingb0000emsl/page/283}}</ref> Some believe that the abundance on Earth is much greater, and that the element's high density has concentrated it in Earth's core.<ref name="patel" /> The free element is not found in nature, but niobium occurs in combination with other elements in minerals.<ref name="Nowak">{{cite journal|title=Niobium Compounds: Preparation, Characterization, and Application in Heterogeneous Catalysis|author=Nowak, Izabela|author2=Ziolek, Maria|journal=Chemical Reviews|date=1999|volume=99|issue=12|pages=3603–3624|doi=10.1021/cr9800208|pmid=11849031}}</ref> Minerals that contain niobium often also contain tantalum. Examples include [[ferrocolumbite]] ({{chem2|(Fe,Mn)Nb2O6}}) and [[coltan]] ({{chem2|(Fe,Mn)(Ta,Nb)2O6}}).<ref name="ICE" /> Columbite–tantalite minerals (the most common species being columbite-(Fe) and tantalite-(Fe)<ref>{{Cite web|url=https://www.mindat.org/min-1514.html|title=Columbite-(Fe): Mineral information, data and localities.|website=www.mindat.org|access-date=6 October 2018|archive-date=18 March 2017|archive-url=https://web.archive.org/web/20170318085151/https://www.mindat.org/min-1514.html|url-status=live}}</ref><ref>{{Cite web|url=https://www.mindat.org/min-1530.html|title=Tantalite-(Fe): Mineral information, data and localities.|website=www.mindat.org|access-date=6 October 2018|archive-date=6 November 2018|archive-url=https://web.archive.org/web/20181106004948/https://www.mindat.org/min-1530.html|url-status=live}}</ref><ref name="nrmima.nrm.se">{{Cite web|url=http://nrmima.nrm.se/|title=CNMNC|website=nrmima.nrm.se|access-date=6 October 2018|archive-url=https://web.archive.org/web/20190810195707/http://nrmima.nrm.se//|archive-date=10 August 2019}}</ref>) that are most usually found as accessory minerals in [[pegmatite]] intrusions, and in alkaline [[intrusive rock]]s. Less common are the niobates of [[calcium]], [[uranium]], [[thorium]] and the [[rare earth element]]s. Examples of such niobates are [[pyrochlore]]s ({{chem2|(Na,Ca)2Nb2O6(OH,F)}})<ref>{{Cite web|url=https://www.mindat.org/min-3316.html|title=Pyrochlore Group: Mineral information, data and localities.|website=www.mindat.org|access-date=6 October 2018|archive-date=19 June 2018|archive-url=https://web.archive.org/web/20180619113047/https://www.mindat.org/min-3316.html|url-status=live}}</ref> and [[euxenite]] ({{chem2|(Y,Ca,Ce,U,Th)(Nb,Ta,Ti)2O6}}). These large deposits of niobium have been found associated with [[carbonatite]]s (carbonate-silicate igneous rocks) and as a constituent of [[pyrochlore]].<ref name="Pyrochlore">{{cite journal|title = Geochemical alteration of pyrochlore group minerals: Pyrochlore subgroup|date = 1995|first = Gregory R.|last = Lumpkin|author2 = Ewing, Rodney C.|journal = American Mineralogist|url = http://www.minsocam.org/msa/AmMin/TOC/Articles_Free/1995/Lumpkin_p732-743_95.pdf|volume = 80|issue = 7–8|pages = 732–743|bibcode = 1995AmMin..80..732L|doi = 10.2138/am-1995-7-810|s2cid = 201657534|access-date = 14 October 2008|archive-date = 17 December 2008|archive-url = https://web.archive.org/web/20081217100545/http://www.minsocam.org/msa/AmMin/TOC/Articles_Free/1995/Lumpkin_p732-743_95.pdf|url-status = live}}</ref><ref>{{Cite web|url=https://www.mindat.org/min-1425.html|title=Euxenite-(Y): Mineral information, data and localities.|website=www.mindat.org|access-date=6 October 2018|archive-date=7 October 2018|archive-url=https://web.archive.org/web/20181007040042/https://www.mindat.org/min-1425.html|url-status=live}}</ref>

The three largest currently mined deposits of pyrochlore, two in Brazil and one in Canada, were found in the 1950s, and are still the major producers of niobium mineral concentrates.<ref name="Gupta" /> The largest deposit is hosted within a carbonatite intrusion in Araxá, state of Minas Gerais, Brazil, owned by CBMM ([[Companhia Brasileira de Metalurgia e Mineração]]); the other active Brazilian deposit is located near Catalão, state of Goiás, and owned by [[China Molybdenum]], also hosted within a carbonatite intrusion.<ref name="tesla" /> Together, those two mines produce about 88% of the world's supply.<ref name="g1">{{cite news |last=Alvarenga |first=Darlan |url=http://g1.globo.com/economia/negocios/noticia/2013/04/monopolio-brasileiro-do-niobio-gera-cobica-mundial-controversia-e-mitos.html |title='Monopólio' brasileiro do nióbio gera cobiça mundial, controvérsia e mitos |language=pt |trans-title=Brazilian niobium 'monopoly' brings about the world's greed, controversy, and myths |work=[[G1 (website)|G1]] |location=São Paulo |date=9 April 2013 |access-date=23 May 2016 |archive-date=29 May 2016 |archive-url=https://web.archive.org/web/20160529175614/http://g1.globo.com/economia/negocios/noticia/2013/04/monopolio-brasileiro-do-niobio-gera-cobica-mundial-controversia-e-mitos.html |url-status=live }}</ref> Brazil also has a large but still unexploited deposit near São Gabriel da Cachoeira, state of Amazonas, as well as a few smaller deposits, notably in the state of Roraima.<ref name="g1" /><ref name="rio negro">{{cite journal|last1=Siqueira-Gay|first1=Juliana |last2=Sánchez| first2=Luis E.|title =Keep the Amazon niobium in the ground|journal= Environmental Science & Policy|volume=111|year= 2020|pages= 1–6|issn=1462-9011|doi =10.1016/j.envsci.2020.05.012 |bibcode=2020ESPol.111....1S |s2cid=219469278 }}</ref>

The third largest producer of niobium is the carbonatite-hosted [[Niobec]] mine, in Saint-Honoré, Quebec, Canada, owned by Magris Resources.<ref name="niobec-magris">{{cite press release |url=http://niobec.com/en/2015/01/magris-resources-officially-owner-of-niobec/ |title=Magris Resources, officially owner of Niobec |publisher=Niobec |date=23 January 2015 |access-date=23 May 2016 |archive-date=5 June 2016 |archive-url=https://web.archive.org/web/20160605092511/http://niobec.com/en/2015/01/magris-resources-officially-owner-of-niobec/ |url-status=live }}</ref> It produces between 7% and 10% of the world's supply.<ref name="tesla">{{cite web|url = http://tesla.desy.de/new_pages/TESLA_Reports/2001/pdf_files/tesla2001-27.pdf|title = Niob für TESLA|access-date = 2 September 2008|first = J.|last = Kouptsidis|author2 = Peters, F.|author3 = Proch, D.|author4 = Singer, W.|publisher = Deutsches Elektronen-Synchrotron DESY|language = de|archive-url = https://web.archive.org/web/20081217100548/http://tesla.desy.de/new_pages/TESLA_Reports/2001/pdf_files/tesla2001-27.pdf|archive-date = 17 December 2008}}</ref><ref name="g1" />

==Production==
[[File:World Niobium Production 2006.svg|upright=1.4|thumb|Niobium producers in 2006 to 2015 |alt=Grey and white world map with Brazil colored red representing 90% of niobium world production and Canada colored in dark blue representing 5% of niobium world production]]

After the separation from the other minerals, the mixed oxides of tantalum  ({{chem2|Ta2O5}}) and niobium ({{chem2|Nb2O5}}) are obtained. The first step in the processing is the reaction of the oxides with hydrofluoric acid:<ref name="ICE" />

:{{chem2|Ta2O5 + 14 HF → 2 H2TaF7 + 5 H2O}}
:{{chem2|Nb2O5 + 10 HF → 2 H2NbOF5 + 3 H2O}}

The first industrial scale separation, developed by Swiss chemist [[Jean Charles Galissard de Marignac]], exploits the differing solubilities of the complex niobium and tantalum fluorides, dipotassium oxypentafluoroniobate monohydrate ({{chem2|K2NbOF5*H2O}}) and dipotassium heptafluorotantalate ({{chem2|K2TaF7}}) in water. Newer processes use the liquid extraction of the fluorides from aqueous solution by organic solvents like [[cyclohexanone]].<ref name="ICE" /> The complex niobium and tantalum fluorides are extracted separately from the organic solvent with water and either precipitated by the addition of [[potassium fluoride]] to produce a potassium fluoride complex, or precipitated with [[ammonia]] as the pentoxide:<ref name="HollemanAF" />

:{{chem2|H2NbOF5 + 2 KF → K2NbOF5↓ + 2 HF}}

Followed by:
:{{chem2|2 H2NbOF5 + 10 NH4OH → Nb2O5↓ + 10 NH4F + 7 H2O}}

Several methods are used for the reduction to metallic niobium. The [[electrolysis]] of a molten mixture of {{chem2|K2NbOF5}} and sodium chloride is one; the other is the reduction of the fluoride with [[sodium]]. With this method, a relatively high purity niobium can be obtained. In large scale production, {{chem2|Nb2O5}} is reduced with hydrogen or carbon.<ref name="HollemanAF" /> In the [[aluminothermic reaction]], a mixture of [[iron oxide]] and niobium oxide is reacted with [[aluminium]]:
:{{chem2|3 Nb2O5 + Fe2O3 + 12 Al → 6 Nb + 2 Fe + 6 Al2O3}}

Small amounts of oxidizers like [[sodium nitrate]] are added to enhance the reaction. The result is [[aluminium oxide]] and [[ferroniobium]], an alloy of iron and niobium used in steel production.<ref>{{cite book|title = Progress in Niobium Markets and Technology 1981–2001|author = Tither, Geoffrey|url = https://www.cbmm.com/portug/sources/techlib/science_techno/table_content/images/pdfs/oppening.pdf |date = 2001| publisher=Niobium 2001 Limited |isbn = 978-0-9712068-0-9|editor = Minerals, Metals and Materials Society|archive-url = https://web.archive.org/web/20081217100553/http://www.cbmm.com.br/portug/sources/techlib/science_techno/table_content/images/pdfs/oppening.pdf|archive-date = 17 December 2008}}</ref><ref>{{cite book|title=The Production of Ferroniobium at the Niobec mine 1981–2001 |first=Claude |last=Dufresne |author2=Goyette, Ghislain |url=https://www.cbmm.com/portug/sources/techlib/science_techno/table_content/sub_1/images/pdfs/start.pdf |date=2001 |publisher=Niobium 2001 Limited |isbn=978-0-9712068-0-9 |editor = Minerals, Metals and Materials Society |archive-url=https://web.archive.org/web/20081217100559/http://www.cbmm.com.br/portug/sources/techlib/science_techno/table_content/sub_1/images/pdfs/start.pdf |archive-date=17 December 2008 }}</ref> Ferroniobium contains between 60 and 70% niobium.<ref name="tesla" /> Without iron oxide, the aluminothermic process is used to produce niobium. Further purification is necessary to reach the grade for superconductive alloys. [[Electron beam melting]] under vacuum is the method used by the two major distributors of niobium.<ref name="Aguly" /><ref name="Chou">{{cite journal|journal = The Iron and Steel Institute of Japan International|volume = 32|date = 1992|issue = 5|doi = 10.2355/isijinternational.32.673|title = Electron Beam Melting and Refining of Metals and Alloys|first = Alok|last = Choudhury|author2=Hengsberger, Eckart |pages = 673–681|doi-access = free}}</ref>

{{as of|2013}}, CBMM from Brazil controlled 85 percent of the world's niobium production.<ref name="lucchesi2013">{{Citation
 |last1=Lucchesi |first1=Cristane |last2=Cuadros|first2=Alex |date=April 2013 |title=Mineral Wealth |type=paper |magazine=[[Bloomberg Markets]] |page=14}}</ref> The [[United States Geological Survey]] estimates that the production increased from 38,700 tonnes in 2005 to 44,500 tonnes in 2006.<ref name="USGSCS2006">{{cite web |url=https://minerals.usgs.gov/minerals/pubs/commodity/niobium/colummcs06.pdf |title=Niobium (Columbium) |first=John F. |last=Papp |publisher=USGS 2006 Commodity Summary |access-date=20 November 2008 |archive-date=17 December 2008 |archive-url=https://web.archive.org/web/20081217100548/http://minerals.usgs.gov/minerals/pubs/commodity/niobium/colummcs06.pdf |url-status=live }}</ref><ref name="USGSCS2007">{{cite web |url=https://minerals.usgs.gov/minerals/pubs/commodity/niobium/colummcs07.pdf |title=Niobium (Columbium) |first=John F. |last=Papp |publisher=USGS 2007 Commodity Summary |access-date=20 November 2008 |archive-date=5 August 2017 |archive-url=https://web.archive.org/web/20170805170910/https://minerals.usgs.gov/minerals/pubs/commodity/niobium/colummcs07.pdf |url-status=live }}</ref> Worldwide resources are estimated to be 4.4 million tonnes.<ref name="USGSCS2007" /> During the ten-year period between 1995 and 2005, the production more than doubled, starting from 17,800 tonnes in 1995.<ref name="USGSCS1997">{{cite web|url = https://minerals.usgs.gov/minerals/pubs/commodity/niobium/230397.pdf|title = Niobium (Columbium)|first = John F.|last = Papp|publisher = USGS 1997 Commodity Summary|access-date = 20 November 2008|archive-date = 11 January 2019|archive-url = https://web.archive.org/web/20190111003407/https://minerals.usgs.gov/minerals/pubs/commodity/niobium/230397.pdf|url-status = live}}</ref> Between 2009 and 2011, production was stable at 63,000 tonnes per year,<ref>[https://minerals.usgs.gov/minerals/pubs/commodity/niobium/mcs-2011-niobi.pdf Niobium (Colombium)] {{Webarchive|url=https://web.archive.org/web/20120708152542/http://minerals.usgs.gov/minerals/pubs/commodity/niobium/mcs-2011-niobi.pdf |date=8 July 2012 }} U.S. Geological Survey, Mineral Commodity Summaries, January 2011</ref> with a slight decrease in 2012 to only 50,000 tonnes per year.<ref>[https://minerals.usgs.gov/minerals/pubs/commodity/niobium/mcs-2016-niobi.pdf Niobium (Colombium)] {{Webarchive|url=https://web.archive.org/web/20160306095041/http://minerals.usgs.gov/minerals/pubs/commodity/niobium/mcs-2016-niobi.pdf |date=6 March 2016 }} U.S. Geological Survey, Mineral Commodity Summaries, January 2016</ref>

{| class="wikitable" style="text-align:right;"
|+ Mine production (t)<ref name="USGSNiobi">{{cite web |author=Cunningham, Larry D. |url=https://minerals.usgs.gov/minerals/pubs/commodity/niobium/ |title=USGS Minerals Information: Niobium (Columbium) and Tantalum |publisher=Minerals.usgs.gov |date=5 April 2012 |access-date=17 August 2012 |archive-date=28 January 2013 |archive-url=https://web.archive.org/web/20130128101220/http://minerals.usgs.gov/minerals/pubs/commodity/niobium/ |url-status=live }}</ref> (USGS estimate)<ref>{{Cite web|url=https://www.usgs.gov/centers/nmic/niobium-columbium-and-tantalum-statistics-and-information|title=Niobium (Columbium) and Tantalum Statistics and Information &#124; U.S. Geological Survey|access-date=2 December 2021|archive-date=6 March 2019|archive-url=https://web.archive.org/web/20190306043939/https://minerals.usgs.gov/minerals/pubs/commodity/niobium/mcs-2019-tanta.pdf|url-status=live}}</ref><ref>{{Cite web|url=https://www.statista.com/statistics/1271222/production-volume-of-niobium-in-nigeria/|title=Nigeria: Production volume of niobium|access-date=2 December 2021|archive-date=2 December 2021|archive-url=https://web.archive.org/web/20211202045325/https://www.statista.com/statistics/1271222/production-volume-of-niobium-in-nigeria/|url-status=live}}</ref>
|-
|| || {{flag|Brazil}} || {{flag|Canada}} || {{flag|Australia}} || {{flag|Nigeria}} || {{flag|Rwanda}} || {{flag|Mozambique}} || {{flag|Democratic Republic of the Congo|name=Congo D.R.}} || [[World]]
|-
|| '''2000''' || 30000 || 2290 || 160 || 35 || 28 || ? || ? || 32600
|-
|| '''2001''' || 22000 || 3200 || 230 || 30 || 120 || ? || 50 || 25600
|-
|| '''2002''' || 26000 || 3410 || 290 || 30 || 76 || 5 || 50 || 29900
|-
|| '''2003''' || 29000 || 3280 || 230 || 190 || 22 || 34 || 13 || 32800
|-
|| '''2004''' || 29900 || 3400 || 200 || 170 || 63 || 130 || 52 || 34000
|-
|| '''2005''' || 35000 || 3310 || 200 || 40 || 63 || 34 || 25 || 38700
|-
|| '''2006''' || 40000 || 4167 || 200 || 35 || 80 || 29 || ? || 44500
|-
|| '''2007''' || 57300 || 3020 || ? || ? || ? || ? || ? || 60400
|-
|| '''2008''' || 58000 || 4380 || ? || ? || ? || ? || ? || 62900
|-
|| '''2009''' || 58000 || 4330 || ? || ? || ? || 4 || ? || 62900
|-
|| '''2010''' || 58000 || 4420 || ? || ? || ? || 10 || ? || 62900
|-
|| '''2011''' || 58000 || 4630 || ? || ? || ? || 29 || ? || 63000
|-
|| '''2012''' || 63000 || 5000 || ? || ? || ? || 30 || ? || 50100
|-
|| '''2013''' || 53100 || 5260 || ? || ? || ? || 20 || ? || 59400
|-
|| '''2014''' || 53000 || 5000 || ? || ? || ? || ? || ? || 59000
|-
|| '''2015''' || 58000 || 5750 || ? || 29 || ? || ? || ? || 64300
|-
|| '''2016''' || 57000 || 6100 || ? || 104 || ? || ? || ? || 63900
|-
|| '''2017''' || 60700 || 6980 || ? || 122 || ? || ? || ? || 69100
|-
|| '''2018''' || 59000 || 7700 || ? || 181 || ? || ? || ? || 68200
|-
|| '''2019''' || 88900 || 6800 || ? || 150 || ? || ? || ? || 97000
|-
|| '''2020''' || 59800 || 6500 || ? || ? || ? || ? || ? || 67700
|}
Lesser amounts are found in Malawi's Kanyika Deposit ([[Kanyika mine]]).

==Compounds==
{{see also|Category:Niobium compounds}}
In many ways, niobium is similar to tantalum and zirconium. It reacts with most nonmetals at high temperatures; with fluorine at room temperature; with [[chlorine]] at {{convert|150|C|F}} and [[hydrogen]] at {{convert|200|C|F}}; and with [[nitrogen]] at {{convert|400|C|F}}, with products that are frequently interstitial and nonstoichiometric.<ref name="Nowak" /> The metal begins to [[oxidation|oxidize]] in air at {{convert|200|C|F}}.<ref name="HollemanAF">{{cite book|publisher = Walter de Gruyter|date = 1985|edition = 91–100|pages = 1075–1079|isbn = 978-3-11-007511-3|title = Lehrbuch der Anorganischen Chemie|author=Holleman, Arnold F.|author2=Wiberg, Egon|author3=Wiberg, Nils|chapter = Niob| language = de}}</ref> It resists corrosion by acids, including [[aqua regia]], [[hydrochloric acid|hydrochloric]], [[sulfuric acid|sulfuric]], [[nitric acid|nitric]] and [[phosphoric acid]]s.<ref name="Nowak" /> Niobium is attacked by hot concentrated sulfuric acid, [[hydrofluoric acid]] and hydrofluoric/nitric acid mixtures. It is also attacked by hot, saturated alkali metal hydroxide solutions.{{citation needed|date=September 2025}}

Although niobium exhibits all of the formal [[oxidation state]]s from +5 to −1, the most common compounds have niobium in the +5 state.<ref name="Nowak" /> Characteristically, compounds in oxidation states less than 5+ display Nb–Nb bonding. In aqueous solutions, niobium only exhibits the +5 oxidation state. It is also readily prone to hydrolysis and is barely soluble in dilute solutions of hydrochloric, sulfuric, nitric and phosphoric acids due to the precipitation of hydrous Nb oxide.<ref name="Aguly" /> Nb(V) is also slightly soluble in alkaline media due to the formation of soluble polyoxoniobate species.<ref>{{Cite journal|last1=Deblonde|first1=Gauthier J. -P.|last2=Chagnes|first2=Alexandre|last3=Bélair|first3=Sarah|last4=Cote|first4=Gérard|date=1 July 2015|title=Solubility of niobium(V) and tantalum(V) under mild alkaline conditions|journal=Hydrometallurgy|volume=156|pages=99–106|doi=10.1016/j.hydromet.2015.05.015|bibcode=2015HydMe.156...99D |issn=0304-386X}}</ref><ref>{{Cite journal|last=Nyman|first=May|date=2 August 2011|title=Polyoxoniobate chemistry in the 21st century|journal=Dalton Transactions|language=en|volume=40|issue=32|pages=8049–8058|doi=10.1039/C1DT10435G|pmid=21670824|issn=1477-9234}}</ref>

===Oxides, niobates and sulfides===
Niobium forms oxides in the oxidation states +5 ([[Niobium pentoxide|{{chem2|Nb2O5}}]]),<ref>{{Cite web|url=https://pubchem.ncbi.nlm.nih.gov/compound/Niobium_oxide#section=Top|title=Niobium oxide {{!}} Nb2O5 – PubChem|last=Pubchem|website=pubchem.ncbi.nlm.nih.gov|access-date=29 June 2016|archive-date=16 August 2016|archive-url=https://web.archive.org/web/20160816070526/https://pubchem.ncbi.nlm.nih.gov/compound/Niobium_oxide#section=Top|url-status=live}}</ref> +4 ([[Niobium dioxide|{{chem2|NbO2}}]]), and the rarer oxidation state, +2 ([[niobium monoxide|NbO]]).<ref>{{Greenwood&Earnshaw}}</ref> Most common is the pentoxide, precursor to almost all niobium compounds and alloys.<ref name="HollemanAF" /><ref name="Cardarelli">{{cite book|first = Francois|last = Cardarelli|date = 2008|title = Materials Handbook |publisher = Springer London|isbn = 978-1-84628-668-1}}</ref> Niobates are generated by dissolving the pentoxide in basic hydroxide solutions or by melting it in alkali metal oxides. Examples are [[lithium niobate]] ({{chem2|LiNbO3}}) and lanthanum niobate ({{chem2|LaNbO4}}). Lithium niobate has a trigonally distorted [[Perovskite (structure)|perovskite]]-like structure, whereas the lanthanum niobate contains lone {{chem|NbO|4|3-}} ions.<ref name="HollemanAF" /> The layered niobium sulfide ({{chem2|NbS2}}) is also known.<ref name="Nowak" />

Materials can be coated with a thin film of niobium(V) oxide [[chemical vapor deposition]] or [[atomic layer deposition]] processes, produced by the thermal decomposition of [[niobium(V) ethoxide]] above {{convert|350|C|F}}.<ref>{{cite thesis | title = Atomic Layer Deposition of High Permittivity Oxides: Film Growth and In Situ Studies |  author = Rahtu, Antti | publisher = University of Helsinki | date = 2002 | isbn = 952-10-0646-3| hdl = 10138/21065 }}</ref><ref>{{cite journal | doi = 10.1149/1.2059247 | title = Electrochromic Properties of Niobium Oxide Thin Films Prepared by Chemical Vapor Deposition | date = 1994 | last1 = Maruyama | first1 = Toshiro | journal = Journal of the Electrochemical Society | volume = 141 | issue = 10 | pages = 2868–2871| bibcode = 1994JElS..141.2868M }}</ref>

===Halides===
[[File:Niobium pentachloride solid.jpg|thumb|right|upright=0.8|A very pure sample of niobium pentachloride|alt=Watch glass on a black surface with a small portion of yellow crystals]]
[[File:Niobium-pentachloride-from-xtal-3D-balls.png|thumb|right|upright=0.8|Ball-and-stick model of niobium pentachloride, which exists as a [[Dimer (chemistry)|dimer]]]]

Niobium forms halides in the oxidation states of +5 and +4 as well as diverse [[nonstoichiometric compound|substoichiometric compounds]].<ref name="HollemanAF" /><ref name="Aguly">{{cite book|first = Anatoly|last = Agulyansky|title = The Chemistry of Tantalum and Niobium Fluoride Compounds|pages = 1–11|publisher = Elsevier|date=2004| isbn = 978-0-444-51604-6}}</ref> The pentahalides ({{chem|NbX|5}}) feature octahedral Nb centres. Niobium pentafluoride ({{chem2|NbF5}}) is a white solid with a melting point of {{convert|79|C|F}} and [[niobium pentachloride]] ({{chem2|NbCl5}}) is yellow (see image at right) with a melting point of {{convert|203.4|C|F}}. Both are [[hydrolyzed]] to give oxides and oxyhalides, such as {{chem2|NbOCl3}}. The pentachloride is a versatile reagent used to generate the [[organometallic]] compounds, such as [[niobocene dichloride]] ({{chem|(C|5|H|5|)|2|NbCl|2}}).<ref>{{cite book|author = Lucas, C. R. |author2 = Labinger, J. A. |author3 = Schwartz, J. |title = Inorganic Syntheses |chapter = Dichlorobis(η <sup>5</sup> -Cyclopentadienyl) Niobium(IV) |editor1-link=Robert Angelici |editor = Robert J. Angelici|date = 1990|volume = 28|pages = 267–270|isbn = 978-0-471-52619-3|doi = 10.1002/9780470132593.ch68|location = New York|publisher=John Wiley & Sons}}</ref> The tetrahalides ({{chem|NbX|4}}) are dark-coloured polymers with Nb-Nb bonds; for example, the black [[hygroscopic]] [[Niobium(IV) fluoride|niobium tetrafluoride]] ({{chem2|NbF4}})<ref>{{Cite journal |last1=Gortsema |first1=F. P. |last2=Didchenko |first2=R. |date=February 1965 |title=The Preparation and Properties of Niobium Tetrafluoride and Oxyfluorides |url=https://pubs.acs.org/doi/abs/10.1021/ic50024a012 |journal=Inorganic Chemistry |language=en |volume=4 |issue=2 |pages=182–186 |doi=10.1021/ic50024a012 |issn=0020-1669|url-access=subscription }}</ref> and dark violet [[Niobium(IV) chloride|niobium tetrachloride]] ({{chem2|NbCl4}}).<ref name="Macintyre">{{cite book |last1=Stirling |first1=V.M. |editor1-last=Macintyre |editor1-first=J.E. |editor2-last=Daniel |editor2-first=F.M. |title=Dictionary of Inorganic Compounds |date=1992 |publisher=CRC Press |location=Cleveland, OH |isbn=978-0-412-30120-9 |page=2957 |edition=1}}</ref>

Anionic halide compounds of niobium are well known, owing in part to the [[Lewis acid]]ity of the pentahalides. The most important is {{chem2|NbF7](2-)}}, an intermediate in the separation of Nb and Ta from the ores.<ref name="ICE">{{cite journal|title = Staff-Industry Collaborative Report: Tantalum and Niobium|author=Soisson, Donald J.|author2=McLafferty, J. J.|author3=Pierret, James A.| journal = Industrial and Engineering Chemistry|date = 1961|volume = 53|issue = 11|pages = 861–868|doi = 10.1021/ie50623a016}}</ref> This heptafluoride tends to form the oxopentafluoride more readily than does the tantalum compound. Other halide complexes include octahedral [{{chem2|NbCl6}}]{{sup|−}}:
:{{chem2|Nb2Cl10 + 2 Cl- → 2 [NbCl6]-}}

As with other metals with low atomic numbers, a variety of reduced halide cluster ions is known, the prime example being {{chem2|[Nb6Cl18](4-)}}.<ref>{{Greenwood&Earnshaw2nd}}</ref>

===Nitrides and carbides===
Other binary compounds of niobium include [[niobium nitride]] (NbN), which becomes a superconductor at low temperatures and is used in detectors for infrared light.<ref>{{cite journal|doi = 10.1080/09500340410001670866|title = Ultrafast superconducting single-photon detectors for near-infrared-wavelength quantum communications|author=Verevkin, A.|display-authors=4|author2=Pearlman, A.|author3=Slstrokysz, W.|author4=Zhang, J.|author5=Currie, M.|author6=Korneev, A.|author7=Chulkova, G.|author8=Okunev, O.|author9=Kouminov, P.|author10=Smirnov, K.|author11=Voronov, B.|author12=N. Gol'tsman, G.|author13=Sobolewski, Roman|journal = Journal of Modern Optics|volume = 51|issue = 12|date = 2004|pages = 1447–1458}}</ref> The main [[niobium carbide]] is NbC, an extremely hard, refractory, [[ceramic]] material, commercially used in cutting tool bits.{{cn|date=September 2025}}

==Applications==
[[File:Niobium metal.jpg|thumb|A niobium foil|alt=Three pieces of metallic foil with yellow taint]]

Out of {{convert|44500|tonne|kg}} of niobium mined in 2006, an estimated 90% was used in high-grade structural steel. The second-largest application is superalloys.<ref name="USGS2006">{{cite web|url = https://minerals.usgs.gov/minerals/pubs/commodity/niobium/myb1-2006-niobi.pdf|title = Niobium (Columbium ) and Tantalum|first = John F.|last = Papp|publisher = USGS 2006 Minerals Yearbook|access-date = 3 September 2008|archive-date = 22 November 2017|archive-url = https://web.archive.org/web/20171122144051/https://minerals.usgs.gov/minerals/pubs/commodity/niobium/myb1-2006-niobi.pdf|url-status = live}}</ref> Niobium alloy superconductors and electronic components account for a very small share of the world production.<ref name="USGS2006" />

===Steel production===
Niobium is an effective [[Microalloyed steel|microalloying]] element for steel, within which it forms niobium carbide and niobium nitride.<ref name="patel" /> These compounds improve the [[grain refining]], and retard recrystallization and [[precipitation hardening]]. These effects in turn increase the toughness, strength, formability, and weldability.<ref name="patel" /> Within microalloyed [[stainless steel]]s, the niobium content is a small (less than 0.1%)<ref name="heister">{{cite book|title = Niobium: Future Possibilities – Technology and the Market Place|first = Friedrich|last = Heisterkamp|author2 = Carneiro, Tadeu|url = https://www.cbmm.com/portug/sources/techlib/science_techno/table_content/images/pdfs/closing.pdf |date = 2001| publisher=Niobium 2001 Limited |isbn = 978-0-9712068-0-9|editor = Minerals, Metals and Materials Society |archive-url = https://web.archive.org/web/20081217100604/http://www.cbmm.com.br/portug/sources/techlib/science_techno/table_content/images/pdfs/closing.pdf|archive-date = 17 December 2008}}</ref> but important addition to high-strength low-alloy steels that are widely used structurally in modern automobiles.<ref name="patel">{{cite journal|journal =Metallurgist|volume = 45|issue = 11–12|doi = 10.1023/A:1014897029026|pages = 477–480|date = 2001|title = Niobium for Steelmaking |first = Zh.|last = Patel|author2=Khul'ka K.|s2cid = 137569464}}</ref> Niobium is sometimes used in considerably higher quantities for highly wear-resistant machine components and knives, as high as 3% in Crucible CPM S110V stainless steel.<ref>{{cite web|title=Datasheet CPM S110V|url=http://www.crucible.com/PDFs/DataSheets2010/Datasheet%20CPM%20S110Vv12010.pdf|publisher=Crucible Industries LLC|access-date=20 November 2017|archive-date=29 March 2017|archive-url=https://web.archive.org/web/20170329130822/http://www.crucible.com/PDFs/DataSheets2010/Datasheet%20CPM%20S110Vv12010.pdf|url-status=live}}</ref>

These same niobium alloys are often used in pipeline construction.<ref name="eggert">{{cite journal|journal = Economic Bulletin|volume = 19|issue = 9|doi = 10.1007/BF02227064|pages = 8–11|date = 1982|title = Niobium: a steel additive with a future|author=Eggert, Peter|author2=Priem, Joachim|author3=Wettig, Eberhard|s2cid = 153775645}}</ref><ref name="Hillenbrand">{{cite journal|url=http://www.europipe.com/files/ep_tp_43_01en.pdf |title=Development and Production of High Strength Pipeline Steels |author=Hillenbrand, Hans-Georg |author2=Gräf, Michael |author3=Kalwa, Christoph |journal=Niobium Science & Technology: Proceedings of the International Symposium Niobium 2001 (Orlando, Florida, USA) |date=2 May 2001 |archive-url=https://web.archive.org/web/20150605054604/http://www.europipe.com/files/ep_tp_43_01en.pdf |archive-date=5 June 2015 }}</ref>

===Superalloys===

Quantities of niobium are used in nickel-, cobalt-, and iron-based superalloys in proportions as great as 6.5%<ref name="heister" /> for such applications as jet engine components, gas turbines, rocket subassemblies, [[turbocharger]] systems, heat resisting, and combustion equipment. Niobium precipitates a hardening γ<nowiki>''</nowiki>-phase within the grain structure of the superalloy.<ref name="Donachie">{{cite book|publisher = ASM International|date = 2002|isbn = 978-0-87170-749-9|title = Superalloys: A Technical Guide|url = https://archive.org/details/superalloystechn00dona|url-access = limited|first = Matthew J.|last = Donachie|pages = [https://archive.org/details/superalloystechn00dona/page/n36 29]–30}}</ref>

One example superalloy is [[inconel|Inconel 718]], consisting of roughly 50% nickel, 18.6% [[chromium]], 18.5% iron, 5% niobium, 3.1% [[molybdenum]], 0.9% titanium, and 0.4% [[aluminium]].<ref name="super">{{cite web|url = http://www.msm.cam.ac.uk/phase-trans/2003/Superalloys/superalloys.html|title = Nickel Based Superalloys|first = H. k. d. h|last = Bhadeshia|publisher = University of Cambridge|access-date = 4 September 2008|archive-url = https://web.archive.org/web/20060825053006/http://www.msm.cam.ac.uk/phase-trans/2003/Superalloys/superalloys.html|archive-date = 25 August 2006}}</ref><ref>{{cite journal|journal = Thermochimica Acta|volume = 382|date = 2002|pages= 55–267|doi = 10.1016/S0040-6031(01)00751-1|title = Thermophysikalische Eigenschaften von festem und flüssigem Inconel 718|language=de|author=Pottlacher, G.|author2=Hosaeus, H.|author3=Wilthan, B.|author4=Kaschnitz, E.|author5=Seifter, A.|issue = 1––2| bibcode=2002TcAc..382..255P }}</ref>

These superalloys were used, for example, in advanced air frame systems for the [[Gemini program]]. Another niobium alloy{{clarify|date=November 2023}} was used for the nozzle of the [[Apollo service module|Apollo Service Module]]. Because niobium is oxidized at temperatures above 400&nbsp;°C, a protective coating is necessary for these applications to prevent the alloy from becoming brittle.<ref name="hightemp" />

===Niobium-based alloys===
{{Main|Niobium alloy}}
[[File:Apollo CSM lunar orbit.jpg|thumb|upright=1.5|[[Apollo 15]] CSM in lunar orbit; dark nozzle of the [[Apollo command and service module#Service propulsion system|service propulsion system]] is made from niobium–titanium alloy |alt=Image of the Apollo Service Module with the moon in the background]]
'''C-103''' alloy was developed in the early 1960s jointly by the [[Wah Chang Corporation]] and [[Boeing]] Co. [[DuPont]], [[Union Carbide]] Corp., [[General Electric]] Co. and several other companies were developing niobium alloys simultaneously, largely driven by the [[Cold War]] and [[Space Race]]. It is composed of 89% niobium, 10% [[hafnium]] and 1% titanium and is used for [[liquid-propellant rocket|liquid-rocket]] thruster nozzles, such as the descent engine of the [[Apollo Lunar Module]]s.<ref name="hightemp">{{cite journal|url=https://www.cbmm.com/portug/sources/techlib/science_techno/table_content/sub_3/images/pdfs/016.pdf |title=Niobium alloys and high Temperature Applications |first=John |last=Hebda |journal=Niobium Science & Technology: Proceedings of the International Symposium Niobium 2001 (Orlando, Florida, USA) |date=2 May 2001 |archive-url=https://web.archive.org/web/20081217080513/http://www.cbmm.com.br/portug/sources/techlib/science_techno/table_content/sub_3/images/pdfs/016.pdf |archive-date=17 December 2008 }}</ref>

The reactivity of niobium with oxygen requires it to be worked in a vacuum or inert atmosphere, which significantly increases the cost and difficulty of production. [[Vacuum arc remelting]] (VAR) and [[electron beam melting]] (EBM), novel processes at the time, enabled the development of niobium and other reactive metals. The project that yielded C-103 began in 1959 with as many as 256 experimental niobium alloys in the "C-series" that could be melted as buttons and rolled into sheet. Wah Chang Corporation had an inventory of hafnium, refined from nuclear-grade zirconium alloys, that it wanted to put to commercial use. The 103rd experimental composition of the C-series alloys, Nb-10Hf-1Ti, had the best combination of formability and high-temperature properties. Wah Chang fabricated the first {{convert|500|lb|kg}} of C-103 in 1961, ingot to sheet, using EBM and VAR. The intended applications included [[Gas turbine|turbine engine]]s and liquid metal [[heat exchanger]]s. Competing niobium alloys from that era included FS85 (Nb-10W-28Ta-1Zr) from [[Fansteel|Fansteel Metallurgical Corp]]., Cb129Y (Nb-10W-10Hf-0.2Y) from Wah Chang and Boeing, Cb752 (Nb-10W-2.5Zr) from Union Carbide, and Nb1Zr from Superior Tube Co.<ref name="hightemp" />

[[File:Merlin nozzle 4105129088 9659a4df4e o.jpg|thumb|[[SpaceX Merlin#Merlin Vacuum (1C)|Merlin Vacuum]] nozzle made from a niobium alloy]]

The nozzle of the Merlin Vacuum series of engines developed by [[SpaceX]] for the upper stage of its [[Falcon 9]] rocket is made from a C-103 niobium alloy.<ref name="NSPO">{{cite conference |title=Low-cost Launch Opportunities Provided by the Falcon Family of Launch Vehicles |first1=Aaron |last1=Dinardi |first2=Peter |last2=Capozzoli |first3=Gwynne |last3=Shotwell |conference=Fourth Asian Space Conference |year=2008 |location=Taipei |url=http://www2.nspo.org.tw/ASC2008/4th%20Asian%20Space%20Conference%202008/oral/S12-11.pdf|archive-url=https://web.archive.org/web/20120315135217/http://www2.nspo.org.tw/ASC2008/4th%20Asian%20Space%20Conference%202008/oral/S12-11.pdf |archive-date=15 March 2012 }}</ref><ref>{{Cite web |last=Jackiewicz |first=Karolina |date=2021-07-21 |title='To boldly go where no man has gone before…', the alloy that has made space travel possible. |url=https://www.lipmann.co.uk/post/to-boldly-go-where-no-man-has-gone-before-the-alloy-that-has-made-space-travel-possible |access-date=2025-04-29 |website=Lipmann Walton & Co |language=en}}</ref>

Niobium-based superalloys are used to produce components of [[Hypersonic weapon|hypersonic missile]] systems.<ref>{{Cite journal |last1=Torres |first1=Guido L. |last2=López |first2=Laura Delgado |last3=Berg |first3=Ryan C. |last4=Ziemer |first4=Henry |date=2024-03-04 |title=Hypersonic Hegemony: Niobium and the Western Hemisphere's Role in the U.S.-China Power Struggle |url=https://www.csis.org/analysis/hypersonic-hegemony-niobium-and-western-hemispheres-role-us-china-power-struggle |language=en |website=CSIS |access-date=Oct 15, 2024}}</ref>

===Superconducting magnets===
[[File:Modern 3T MRI.JPG|right|thumb|A 3-[[Tesla (unit)|tesla]] clinical [[MRI|magnetic resonance imaging]] scanner using niobium superconducting alloy|alt=Room-high yellow-grey medical machine with a man-size hole in the middle and a stretcher directly in front of it]]

[[Niobium-germanium]] ({{chem2|Nb3Ge}}), [[niobium–tin]] ({{chem2|Nb3Sn}}), as well as the [[niobium–titanium]] alloys are used as a type II superconductor wire for superconducting magnets.<ref>{{cite journal|doi = 10.1109/77.828394|title = Powder-in-tube (PIT) Nb/sub 3/Sn conductors for high-field magnets|date = 2000|author = Lindenhovius, J.L.H.|journal = IEEE Transactions on Applied Superconductivity|volume = 10|issue = 1|pages = 975–978|display-authors = 4|last2 = Hornsveld|first2 = E. M.|last3 = Den Ouden|first3 = A.|last4 = Wessel|first4 = W. A. J.|last5 = Ten Kate|first5 = H. H. J.|bibcode = 2000ITAS...10..975L|s2cid = 26260700|url = https://ris.utwente.nl/ws/files/176419956/00828394.pdf|archive-date = 17 September 2023|access-date = 29 August 2023|archive-url = https://web.archive.org/web/20230917220838/https://ris.utwente.nl/ws/files/176419956/00828394.pdf}}</ref><ref>{{cite web|url = http://hyperphysics.phy-astr.gsu.edu/Hbase/solids/scmag.html|title = Superconducting Magnets|first = Carl R.|last = Nave|publisher = Georgia State University, Department of Physics and Astronomy|access-date = 25 November 2008|archive-date = 5 December 2008|archive-url = https://web.archive.org/web/20081205013800/http://hyperphysics.phy-astr.gsu.edu/hbase/solids/scmag.html|url-status = live}}</ref> These superconducting magnets are used in magnetic resonance imaging and [[nuclear magnetic resonance]] instruments as well as in [[particle accelerator]]s.<ref>{{cite journal|journal = Physica C: Superconductivity|volume= 372–376|issue = 3|date = 2002|pages = 1315–1320|doi = 10.1016/S0921-4534(02)01018-3|title = Niobium based intermetallics as a source of high-current/high magnetic field superconductors|first=B. A.|last = Glowacki|author2=Yan, X. -Y. |author3=Fray, D. |author4=Chen, G. |author5=Majoros, M. |author6= Shi, Y. |arxiv = cond-mat/0109088 |bibcode = 2002PhyC..372.1315G |s2cid= 118990555}}</ref> For example, the [[Large Hadron Collider]] uses {{convert|600|ST|kg}} of superconducting strands, while the [[International Thermonuclear Experimental Reactor]] uses an estimated {{convert|600|LT|kg}} of {{chem2|Nb3Sn}} strands and {{convert|250|LT|kg}} of NbTi strands.<ref name="alstrom">{{cite journal|journal = Fusion Engineering and Design (Proceedings of the 23rd Symposium of Fusion Technology)|volume= 75–79|issue= 2|date = 2005|page = 3516|title = A success story: LHC cable production at ALSTOM-MSA|author=Grunblatt, G.|author2=Mocaer, P.|author3=Verwaerde Ch.|author4=Kohler, C.| doi = 10.1016/j.fusengdes.2005.06.216|bibcode= 2005ITAS...15.3516M|s2cid= 41810761}}</ref> In 1992 alone, more than one billion US dollars' worth of clinical magnetic resonance imaging systems were constructed with niobium-titanium wire.<ref name="geballe" />

====Other superconductors====
[[File:A 1.3 GHz nine-cell superconducting radio frequency.JPG|thumb|A {{val|1.3|u=GHz}} 9-cell superconducting radio frequency cavity made from niobium is on display at Fermilab]]

The [[superconducting radio frequency]] (SRF) cavities used in the [[free-electron laser]]s [[FLASH]] (result of the cancelled TESLA linear accelerator project) and [[European x-ray free electron laser|XFEL]] are made from pure niobium.<ref>{{cite journal|journal = Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment|volume = 524|date = 2004|pages = 1–12|doi = 10.1016/j.nima.2004.01.045|title = Achievement of 35 MV/m in the superconducting nine-cell cavities for TESLA|author=Lilje, L.|display-authors=4|author2=Kako, E.|author3=Kostin, D.|author4=Matheisen, A.|author5=Möller, W.-D.|author6=Proch, D.|author7=Reschke, D.|author8=Saito, K.|author9=Schmüser, P.|author10=Simrock, S.|author11=Suzuki T.|author12=Twarowski, K.|issue = 1–3|arxiv = physics/0401141 |bibcode = 2004NIMPA.524....1L |s2cid = 2141809}}</ref> A cryomodule team at [[Fermilab]] used the same SRF technology from the FLASH project to develop {{val|1.3|u=GHz}} nine-cell SRF cavities made from pure niobium. The cavities will be used in the {{Convert|30|km|adj=on}} linear particle accelerator of the [[International Linear Collider]].<ref>{{cite book|title=The International Linear Collider Technical Design Report 2013|date=2013|publisher=International Linear Collider|url=http://edmsdirect.desy.de/edmsdirect/file.jsp?edmsid=D00000001021265&fileClass=native|access-date=15 August 2015|archive-date=30 September 2015|archive-url=https://web.archive.org/web/20150930150054/http://edmsdirect.desy.de/edmsdirect/file.jsp?edmsid=D00000001021265&fileClass=native|url-status=live}}</ref> The same technology will be used in [[LCLS-II]] at [[SLAC National Accelerator Laboratory]] and [[PIP-II]] at Fermilab.<ref>{{cite news|title=ILC-type cryomodule makes the grade|url=http://cerncourier.com/cws/article/cern/59319|access-date=15 August 2015|work=CERN Courier|publisher=IOP Publishing|date=27 November 2014|archive-date=5 March 2016|archive-url=https://web.archive.org/web/20160305131621/http://cerncourier.com/cws/article/cern/59319|url-status=live}}</ref>

The high sensitivity of superconducting niobium nitride [[bolometer]]s make them an ideal detector for [[electromagnetic radiation]] in the THz frequency band. These detectors were tested at the [[Heinrich Hertz Submillimeter Telescope]], the [[South Pole Telescope]], the Receiver Lab Telescope, and at [[Atacama Pathfinder Experiment]] (APEX), and are now used in the HIFI instrument on board the [[Herschel Space Observatory]].<ref>{{cite journal|journal = Review of Scientific Instruments|volume = 79|date = 2008|pages = 0345011–03451010|doi = 10.1063/1.2890099|title = A Hot-electron bolometer terahertz mixers for the Herschel Space Observatory|author=Cherednichenko, Sergey|display-authors=4|author2=Drakinskiy, Vladimir|author3=Berg, Therese|author4=Khosropanah, Pourya|author5=Kollberg, Erik|pmid = 18377032|issue = 3|bibcode = 2008RScI...79c4501C }}</ref>

===Other uses===
====Electroceramics====
Lithium niobate, which is a [[ferroelectric]], is used extensively in mobile telephones and [[optical modulators]], and for the manufacture of [[surface acoustic wave]] devices. It belongs to the perovskite ({{chem2|ABO3}}) structure ferroelectrics like [[lithium tantalate]] and [[barium titanate]].<ref>{{cite book|title = Lithium Niobate: Defects, Photorefraction and Ferroelectric Switching|url = https://archive.org/details/lithiumniobatede00volk_393|url-access = limited|first = Tatyana|last = Volk|author2=Wohlecke, Manfred |publisher = Springer|date = 2008|isbn = 978-3-540-70765-3|pages = [https://archive.org/details/lithiumniobatede00volk_393/page/n12 1]–9}}</ref> [[Niobium capacitor]]s are available as alternatives to [[tantalum capacitor]]s,<ref>{{cite journal|journal = Quality and Reliability Engineering International|volume = 14|issue = 2|doi = 10.1002/(SICI)1099-1638(199803/04)14:2<79::AID-QRE163>3.0.CO;2-Y|pages = 79–82|date = 1991 |title = Reliability comparison of tantalum and niobium solid electrolytic capacitors|first = Y.|last = Pozdeev|doi-access = free}}</ref> but tantalum capacitors still predominate.{{cn|date=September 2025}} Niobium is added to glass to obtain a higher [[refractive index]], making possible thinner and lighter corrective lenses for eyeglasses.{{cn|date=September 2025}}

====Hypoallergenic applications: medicine and jewelry====
Niobium and some niobium alloys are physiologically inert and [[hypoallergenic]]. For this reason, niobium is used in prosthetics and implant devices, such as pacemakers.<ref>{{cite journal|author=Mallela, Venkateswara Sarma|author2=Ilankumaran, V.|author3=Srinivasa Rao, N.| title = Trends in Cardiac Pacemaker Batteries|journal = Indian Pacing Electrophysiol J|volume = 4|issue = 4|pages = 201–212|date=1 January 2004|pmid = 16943934|pmc = 1502062}}</ref> Niobium treated with sodium hydroxide forms a porous layer that aids [[osseointegration]].<ref>{{cite journal|author=Godley, Reut|author2=Starosvetsky, David|author3=Gotman, Irena|date = 2004|title = Bonelike apatite formation on niobium metal treated in aqueous NaOH|journal = Journal of Materials Science: Materials in Medicine|volume = 15|pages = 1073–1077|doi = 10.1023/B:JMSM.0000046388.07961.81|pmid = 15516867|issue = 10|s2cid=44988090}}</ref>

Like titanium, tantalum, and aluminium, niobium can be heated and [[anodize]]d to produce a wide array of [[Iridescence|iridescent]] colours for jewelry, where its hypoallergenic property is highly desirable.<ref>{{cite journal|journal = Journal of Applied Electrochemistry|volume = 21|issue = 11|doi = 10.1007/BF01077589|pages = 1023–1026 |date = 1991|title = Anodization of niobium in sulphuric acid media|author=Biason Gomes, M. A.|author2=Onofre, S.|author3=Juanto, S.|author4=Bulhões, L. O. de S.|s2cid = 95285286}}</ref><ref>{{cite journal|journal = Thin Solid Films|volume = 8|issue = 4|doi = 10.1016/0040-6090(71)90027-7|pages = R37–R39|date = 1971|title = A note on the thicknesses of anodized niobium oxide films|first = Y. L.|last = Chiou|bibcode = 1971TSF.....8R..37C }}</ref><ref>{{cite journal|doi = 10.1361/152981502770351860|author=Azevedo, C. R. F.|author2=Spera, G.|author3=Silva, A. P.|title = Characterization of metallic piercings that caused adverse reactions during use|journal = Journal of Failure Analysis and Prevention|volume = 2|issue = 4|pages = 47–53|date =2002}}</ref>

====Numismatics====
Niobium is used as a precious metal in commemorative coins, often with [[silver]] or [[gold]]. For example, Austria produced a series of silver niobium euro (€) coins starting in 2003; the colour in these coins is created by the [[diffraction]] of light by a thin anodized oxide layer.<ref>{{cite journal|doi = 10.1016/j.ijrmhm.2005.10.008|journal = International Journal of Refractory Metals and Hard Materials|volume = 24|issue = 4|date = 2006|pages = 275–282|title = Niobium as mint metal: Production–properties–processing|first =Robert|last = Grill|author2=Gnadenberge, Alfred }}</ref> In 2012, ten coins are available showing a broad variety of colours in the centre of the coin: blue, green, brown, purple, violet, or yellow. Two more examples are the 2004 Austrian €25 [[Euro gold and silver commemorative coins (Austria)#2004 coinage|150-Year Semmering Alpine Railway commemorative coin]],<ref>{{cite web|url =http://austrian-mint.at/bimetallmuenzen?l=en&muenzeSubTypeId=113&muenzeId=217|archive-url =https://web.archive.org/web/20110721053534/http://austrian-mint.at/bimetallmuenzen?l=en&muenzeSubTypeId=113&muenzeId=217|archive-date=21 July 2011|title = 25 Euro – 150 Years Semmering Alpine Railway (2004)|access-date=4 November 2008|publisher = [[Austrian Mint]]}}</ref> and the 2006 Austrian €25 [[Euro gold and silver commemorative coins (Austria)#2006 coinage|European Satellite Navigation commemorative coin]].<ref>{{cite web|url =http://www.austrian-mint.at/cms/download.php?downloadId=131|archive-url =https://web.archive.org/web/20110720002739/http://www.austrian-mint.at/cms/download.php?downloadId=131|archive-date=20 July 2011|title = 150 Jahre Semmeringbahn|access-date=4 September 2008| publisher = [[Austrian Mint]]| language=de}}</ref> The Austrian mint produced for Latvia a similar series of coins starting in 2004,<ref>{{cite web|url =http://www.bank.lv/eng/main/all/lvnaud/jubmon/nmp/time/|archive-url =https://web.archive.org/web/20080109033431/http://www.bank.lv/eng/main/all/lvnaud/jubmon/nmp/time/ |archive-date=9 January 2008 |title = Neraža – mēs nevarējām atrast meklēto lapu!|language=lv|access-date=19 September 2008|publisher = Bank of Latvia}}</ref> with one following in 2007.<ref>{{cite web|url = http://www.bank.lv/eng/main/all/lvnaud/jubmon/nmp/time2/|archive-url = https://web.archive.org/web/20090522101540/http://www.bank.lv/eng/main/all/lvnaud/jubmon/nmp/time2/|archive-date=22 May 2009|title = Neraža – mēs nevarējām atrast meklēto lapu!|language=lv|access-date=19 September 2008|publisher = Bank of Latvia}}</ref> In 2011, the Royal Canadian Mint started production of a $5 sterling silver and niobium coin named ''Hunter's Moon'' in which the niobium was selectively oxidized, thus creating unique finishes where no two coins are exactly alike.<ref>{{Cite web|url=https://www.mint.ca/en/shop/coins/2011/sterling-silver-and-niobium-coin---hunters-moon-2011|title=$5 Sterling Silver and Niobium Coin – Hunter's Moon (2011)|publisher=Royal Canadian Mint|access-date=23 October 2025|archive-date=25 February 2014|archive-url=https://web.archive.org/web/20140225232038/http://www.mint.ca/store/coin/5-sterling-silver-and-niobium-coin-hunters-moon-2011-prod1110013|url-status=live}}</ref>

[[File:2004 Austria 25 Euro 150 Years Semmering Alpine Railway front.jpg|thumb|right|A 150 Years Semmering Alpine Railway Coin made of niobium and silver |alt=Coin with a dark green center and a silvery outer rim. The rim reads: Republik Österreich 25 Euro. The centere shows electric and a steam driven locomotive]]

====Other====
The arc-tube seals of high pressure [[sodium vapor lamp]]s are made from niobium, sometimes alloyed with 1% of zirconium; niobium has a very similar coefficient of thermal expansion, matching the [[sintered]] [[alumina]] [[arc tube]] ceramic, a translucent material which resists chemical attack or reduction by the hot liquid sodium and sodium vapour contained inside the operating lamp.<ref>{{cite book|title = Lamps and Lighting|author=Henderson, Stanley Thomas|author2=Marsden, Alfred Michael|author3=Hewitt, Harry|publisher = Edward Arnold Press|date = 1972|isbn = 978-0-7131-3267-0|pages = 244–245}}</ref><ref>{{cite journal|title = Refractory metals: crucial components for light sources|last = Eichelbrönner|first = G.|date =1998|journal = International Journal of Refractory Metals and Hard Materials|volume = 16|issue = 1|pages = 5–11|doi = 10.1016/S0263-4368(98)00009-2}}</ref><ref>{{cite book|title = Niobium and Niobium 1% Zirconium for High Pressure Sodium (HPS) Discharge Lamps|author=Michaluk, Christopher A.|author2=Huber, Louis E.|author3=Ford, Robert B. |date = 2001|publisher=Niobium 2001 Limited |isbn = 978-0-9712068-0-9 |editor = Minerals, Metals and Materials Society}}</ref>

Niobium is used in [[arc welding]] rods for some stabilized grades of stainless steel<ref>{{US patent reference|number = 5254836|issue-date=19 October 1993|inventor = Okada, Yuuji; Kobayashi, Toshihiko; Sasabe, Hiroshi; Aoki, Yoshimitsu; Nishizawa, Makoto; Endo, Shunji|title = Method of arc welding with a ferrite stainless steel welding rod}}</ref>{{better citation needed|reason=Patent does not equal actual use|date=September 2025}} and in anodes for cathodic protection systems on some water tanks, which are then usually plated with platinum.<ref>{{cite book|author=Moavenzadeh, Fred|title=Concise Encyclopedia of Building and Construction Materials|url=https://books.google.com/books?id=YiJaEAUj258C&pg=PA157|access-date=18 February 2012|date=14 March 1990|publisher=MIT Press|isbn=978-0-262-13248-0|pages=157–|archive-date=3 June 2013|archive-url=https://web.archive.org/web/20130603023711/http://books.google.com/books?id=YiJaEAUj258C&pg=PA157|url-status=live}}</ref><ref>{{cite book|author=Cardarelli, François|title=Materials handbook: a concise desktop reference|url=https://books.google.com/books?id=PvU-qbQJq7IC&pg=PA352|access-date=18 February 2012|date=9 January 2008|publisher=Springer|isbn=978-1-84628-668-1|pages=352–|archive-date=3 June 2013|archive-url=https://web.archive.org/web/20130603004328/http://books.google.com/books?id=PvU-qbQJq7IC&pg=PA352|url-status=live}}</ref>

Niobium is used to make the high voltage wire of the [[solar corona]] particles receptor module of the [[Parker Solar Probe]].<ref>{{cite AV media |people=Dr. Tony Case |date=24 August 2018 |title=Scientist Interview: Dr. Tony Case (Parker Solar Probe) |language=en |url=https://www.youtube.com/watch?v=m3GKfvPc2ns&t=214s | archive-url=https://ghostarchive.org/varchive/youtube/20211107/m3GKfvPc2ns| archive-date=2021-11-07 | url-status=live|access-date=24 August 2018}}{{cbignore}}</ref>

Niobium is a constituent of a lightfast chemically stable inorganic yellow pigment that has the trade name NTP Yellow. It is Niobium Sulfur Tin Zinc Oxide, a [[pyrochlore]], produced via high-temperature [[calcination]]. The pigment is also known as pigment yellow 227, commonly listed as PY 227 or PY227.<ref>{{cite web |title=The Color of Art Pigment Database – Pigment Yellow – PY |date=2024 |website=artiscreation |url=https://www.artiscreation.com/yellow.html#PY227 |access-date=2024-08-17 }}</ref>

Niobium is employed in the atomic energy industry for its high temperature and corrosion resistance, as well as its stability under [[radiation]].<ref>{{cite journal |last1=Shen |first1=Zhipeng |last2=Wang |first2=Tao |year=2024 |title=Irradiation resistance of a novel multi-component Nb alloy at elevated temperature |journal=Materials Characterization |volume=214 |article-number=114102 |doi=10.1016/j.matchar.2024.114102}}</ref> It is used in [[nuclear reactors]] for components like fuel rods and reactor cores.<ref>{{cite web |url=https://www.refractorymetal.org/uses-of-niobium/ |title=10 Important Uses of Niobium |website=Advanced Refractory Metals |date=2 April 2020 |access-date=Oct 15, 2024}}</ref><ref>{{cite journal |last1=Sathers |first1=D. |last2=Flanigan |first2=J. |year=2022 |title=Niobium rod quality and its impact on the production of Nb3Sn strand for the Divertor Tokamak Test Facility toroidal coils |journal=IOP Conference Series: Materials Science and Engineering |volume=1241 |article-number=012017 |doi=10.1088/1757-899X/1241/1/012017|doi-access=free }}</ref>

Nickel niobium alloys are used in aerospace, oil and gas, construction. They are used in components of jet engines, in ground gas turbines, elements of bridges and high-rise buildings.<ref>{{Cite web |last=Schmitz |first=Sophia |date=2025-04-28 |title=Nickel Niobium Market Expected to Reach $2.5 Billion by 2034 as Demand Rises in Aerospace and Automotive Sectors |url=https://metals-wire.net/commodities/nickel-niobium-market-expected-to-reach-2-5-billion-by-2034-as-demand-rises-in-aerospace-and-automotive-sectors/ |access-date=2025-04-29 |website=Metals Wire |language=en}}</ref><ref>{{Cite news |last1=Smith |first1=G. D. |last2=Patel |first2=S. J. |title=The role of niobium in wrought precipitation-hardened nickel-base alloys |url=https://www.tms.org/Superalloys/10.7449/2005/Superalloys_2005_135_154.pdf |work=The Minerals, Metals & Materials Society|date=2005 |pages=135–154 |doi=10.7449/2005/Superalloys_2005_135_154 |isbn=978-0-87339-602-8 }}</ref>

==Precautions==
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Niobium has no known biological role. While niobium dust is an eye and skin irritant and a potential fire hazard, elemental niobium on a larger scale is physiologically inert (and thus hypoallergenic) and harmless. It is often used in jewelry and has been tested for use in some medical implants.<ref>{{cite journal|title = New trends in the use of metals in jewellery|author=Vilaplana, J.|author2=Romaguera, C.|author3=Grimalt, F.|author4=Cornellana, F.|journal = Contact Dermatitis|volume = 25|issue = 3 |pages = 145–148|date = 1990|doi = 10.1111/j.1600-0536.1991.tb01819.x|pmid = 1782765|s2cid=30201028|doi-access = free}}</ref><ref>{{cite journal|title = New developments in jewellery and dental materials|first = J.|last = Vilaplana|author2=Romaguera, C. | journal = Contact Dermatitis|volume = 39|issue = 2| pages = 55–57|date = 1998|doi = 10.1111/j.1600-0536.1998.tb05832.x|pmid = 9746182|s2cid = 34271011}}</ref>

Short- and long-term exposure to niobates and niobium chloride, two water-soluble chemicals, have been tested in rats. Rats treated with a single injection of niobium pentachloride or niobates show a [[median lethal dose]] (LD{{sub|50}}) between 10 and 100&nbsp;mg/kg.<ref name="Haley">{{cite journal|title = Pharmacology and toxicology of niobium chloride|author=Haley, Thomas J.|author2=Komesu, N.|author3=Raymond, K.|journal = [[Toxicology and Applied Pharmacology]]|volume = 4|issue = 3|pages = 385–392|date = 1962|doi = 10.1016/0041-008X(62)90048-0|pmid=13903824|bibcode=1962ToxAP...4..385H }}</ref><ref>{{cite journal|title = The Toxicity of Niobium Salts |author=Downs, William L. |display-authors=4 |author2=Scott, James K. |author3=Yuile, Charles L. |author4=Caruso, Frank S. |author5=Wong, Lawrence C. K.|journal = American Industrial Hygiene Association Journal|volume = 26|issue = 4|pages = 337–346|date = 1965|doi = 10.1080/00028896509342740|pmid = 5854670}}</ref><ref>{{cite journal|title = Zirconium, Niobium, Antimony, Vanadium and Lead in Rats: Life term studies|author=Schroeder, Henry A.|author2=Mitchener, Marian|author3=Nason, Alexis P.|journal = Journal of Nutrition|volume = 100|issue = 1|pages = 59–68|date=1970|pmid =5412131|doi=10.1093/jn/100.1.59|s2cid=4444415|url = https://pdfs.semanticscholar.org/7730/157588b8312d9076f95fcfb78d404a893033.pdf|archive-url = https://web.archive.org/web/20200219052439/https://pdfs.semanticscholar.org/7730/157588b8312d9076f95fcfb78d404a893033.pdf|archive-date = 2020-02-19}}</ref> For oral administration the toxicity is lower; a study with rats yielded a LD{{sub|50}} after seven days of {{val|940|u=mg/kg}}.<ref name="Haley" />
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==References==
{{Reflist|30em}}

==External links==
{{Commons|Niobium}}
{{Wiktionary|niobium}}
* [http://www.tanb.org/ Tantalum-Niobium International Study Center]
* [https://web.archive.org/web/20061002182416/http://www.symmetrymag.org/cms/?pid=1000173 Niobium for particle accelerators eg ILC. 2005]
* {{cite EB9 |wstitle = Niobium |volume= XVII | page=513 |short=1 }}
* {{Cite NIE|wstitle=Columbium|short=1}}
* {{Cite EB1911|wstitle=Columbium|short=x}}
* [http://www.periodicvideos.com/videos/041.htm Niobium] at ''[[The Periodic Table of Videos]]'' (University of Nottingham)

{{Periodic table (navbox)}}
{{Niobium compounds}}
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[[Category:Niobium| ]]
[[Category:Chemical elements]]
[[Category:Chemical elements with body-centered cubic structure]]
[[Category:Native element minerals]]
[[Category:Refractory metals]]
[[Category:Transition metals]]