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Niobium,  41Nb
Niobium crystals and 1cm3 cube.jpg
Pronunciation /nˈbiəm/ (ny-OH-bee-əm)
Appearancegray metallic, bluish when oxidized
Standard atomic weight Ar, std(Nb)92.90637(1) [1]
Niobium in the periodic table
Hydrogen Helium
Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon
Sodium Magnesium Aluminium Silicon Phosphorus Sulfur Chlorine Argon
Potassium Calcium Scandium Titanium Vanadium Chromium Manganese Iron Cobalt Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton
Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine Xenon
Caesium Barium Lanthanum Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercury (element) Thallium Lead Bismuth Polonium Astatine Radon
Francium Radium Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium Rutherfordium Dubnium Seaborgium Bohrium Hassium Meitnerium Darmstadtium Roentgenium Copernicium Nihonium Flerovium Moscovium Livermorium Tennessine Oganesson


Atomic number (Z)41
Group group 5
Period period 5
Block d-block
Element category   Transition metal
Electron configuration [ Kr ] 4d4 5s1
Electrons per shell
2, 8, 18, 12, 1
Physical properties
Phase at  STP solid
Melting point 2750  K (2477 °C,4491 °F)
Boiling point 5017 K(4744 °C,8571 °F)
Density (near r.t.)8.57 g/cm3
Heat of fusion 30  kJ/mol
Heat of vaporization 689.9 kJ/mol
Molar heat capacity 24.60 J/(mol·K)
Vapor pressure
P (Pa)1101001 k10 k100 k
at T (K)294232073524391043935013
Atomic properties
Oxidation states −3, −1, +1, +2, +3, +4, +5 (a mildly acidic oxide)
Electronegativity Pauling scale: 1.6
Ionization energies
  • 1st: 652.1 kJ/mol
  • 2nd: 1380 kJ/mol
  • 3rd: 2416 kJ/mol
Atomic radius empirical:146  pm
Covalent radius 164±6 pm
Color lines in a spectral range Niobium spectrum visible.png
Color lines in a spectral range
Spectral lines of niobium
Other properties
Natural occurrence primordial
Crystal structure body-centered cubic (bcc)
Speed of sound thin rod3480 m/s(at 20 °C)
Thermal expansion 7.3 µm/(m·K)
Thermal conductivity 53.7 W/(m·K)
Electrical resistivity 152 nΩ·m(at 0 °C)
Magnetic ordering paramagnetic
Young's modulus 105 GPa
Shear modulus 38 GPa
Bulk modulus 170 GPa
Poisson ratio 0.40
Mohs hardness 6.0
Vickers hardness 870–1320 MPa
Brinell hardness 735–2450 MPa
CAS Number 7440-03-1
Namingafter Niobe in Greek mythology, daughter of Tantalus (tantalum)
Discovery Charles Hatchett (1801)
First isolation Christian Wilhelm Blomstrand (1864)
Recognized as a distinct element by Heinrich Rose (1844)
Main isotopes of niobium
Iso­tope Abun­dance Half-life (t1/2) Decay mode Pro­duct
90Nb syn 15 h β+ 90Zr
91Nbsyn680 y ε 91Zr
91m Nbsyn61 d IT 91Nb
92m1Nbsyn10 dε 92Zr
92Nb trace 3.47×107 yε92Zr
93Nb100% stable
93mNbsyn16 yIT 93Nb
94Nbtrace20.3×103 y β 94Mo
95Nbsyn35 dβ 95Mo
95mNbsyn4 dIT 95Nb
96Nbsyn24 hβ 96Mo
| references

Niobium, formerly known as columbium, is a chemical element with the symbol Nb (formerly Cb) and atomic number 41. Niobium is a light grey, crystalline, and ductile transition metal. Pure niobium has a hardness similar to that of pure titanium [ contradictory ], [2] and it has similar ductility to iron. Niobium oxidizes in the 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, hence the former name "columbium". Its name comes from Greek mythology, specifically Niobe, who was the daughter of Tantalus, the namesake of tantalum. The name reflects the great similarity between the two elements in their physical and chemical properties, making them difficult to distinguish. [3]

Chemical element a species of atoms having the same number of protons in the atomic nucleus

A chemical element is a species of atom having the same number of protons in their atomic nuclei. For example, the atomic number of oxygen is 8, so the element oxygen consists of all atoms which have 8 protons.

Symbol (chemistry) an arbitrary or conventional sign used in chemical science to represent a chemical element

In chemistry, a symbol is an abbreviation for a chemical element. Symbols for chemical elements normally consist of one or two letters from the Latin alphabet and are written with the first letter capitalised.

Atomic number number of protons found in the nucleus of an atom

The atomic number or proton number of a chemical element is the number of protons found in the nucleus of every atom of that element. The atomic number uniquely identifies a chemical element. It is identical to the charge number of the nucleus. In an uncharged atom, the atomic number is also equal to the number of electrons.


The English chemist Charles Hatchett reported a new element similar to tantalum in 1801 and named it columbium. In 1809, the English chemist William Hyde Wollaston wrongly concluded that tantalum and columbium were identical. The 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.

Charles Hatchett British chemist

Charles Hatchett FRS FRSE was a British chemist who discovered the element niobium.

William Hyde Wollaston Scientist, physicist

William Hyde Wollaston was an English chemist and physicist who is famous for discovering the chemical elements palladium and rhodium. He also developed a way to process platinum ore into malleable ingots.

Heinrich Rose German chemist

Heinrich Rose was a German mineralogist and analytical chemist. He was the brother of the mineralogist Gustav Rose and a son of Valentin Rose.

It was not until the early 20th century that niobium was first used commercially. 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. The temperature stability of niobium-containing superalloys is important for its use in jet and rocket engines.

Ferroniobium is an important iron niobium alloy, with a niobium content of 60-70%. It is the main source for niobium alloying of HSLA steel and covers more than 80% of the worldwide niobium production. The niobium is mined from pyrochlore deposits and is subsequently transformed into the niobium pentoxide Nb2O5. This oxide is mixed with iron oxide and aluminium and is reduced in an aluminothermic reaction to niobium and iron. The component metals can be purified in an electron beam furnace or the alloy can be used as it is. For alloying with steel the ferroniobium is added to molten steel before casting. The largest producers of ferroniobium are the same as for niobium and are located in Brazil and Canada.

Alloy mixture or metallic solid solution composed of two or more elements

An alloy is a combination of metals or a combination of one or more metals with non-metallic elements. For example, combining the metallic elements gold and copper produces red gold, gold and silver becomes white gold, and silver combined with copper produces sterling silver. Elemental iron, combined with non-metallic carbon or silicon, produces alloys called steel or silicon steel. The resulting mixture forms a substance with properties that often differ from those of the pure metals, such as increased strength or hardness. Unlike other substances that may contain metallic bases but do not behave as metals, such as aluminium oxide (sapphire), beryllium aluminium silicate (emerald) or sodium chloride (salt), an alloy will retain all the properties of a metal in the resulting material, such as electrical conductivity, ductility, opaqueness, and luster. Alloys are used in a wide variety of applications, from the steel alloys, used in everything from buildings to automobiles to surgical tools, to exotic titanium-alloys used in the aerospace industry, to beryllium-copper alloys for non-sparking tools. In some cases, a combination of metals may reduce the overall cost of the material while preserving important properties. In other cases, the combination of metals imparts synergistic properties to the constituent metal elements such as corrosion resistance or mechanical strength. Examples of alloys are steel, solder, brass, pewter, duralumin, bronze and amalgams.

Steel alloy made by combining iron and other elements

Steel is an alloy of iron and carbon, and sometimes other elements. Because of its high tensile strength and low cost, it is a major component used in buildings, infrastructure, tools, ships, automobiles, machines, appliances, and weapons.

Niobium is used in various superconducting materials. These superconducting alloys, also containing titanium and tin, are widely used in the superconducting magnets of MRI scanners. Other applications of niobium include welding, nuclear industries, electronics, optics, numismatics, and jewelry. In the last two applications, the low toxicity and iridescence produced by anodization are highly desired properties. Niobium is considered a technology-critical element.

Superconductivity Electrical conductivity with almost zero resistance.

Superconductivity is the set of physical properties observed in certain materials, wherein electrical resistance vanishes and from which magnetic flux fields are expelled. Any material exhibiting these properties is a superconductor. Unlike an ordinary metallic conductor, whose resistance decreases gradually as its temperature is lowered even down to near absolute zero, a superconductor has a characteristic critical temperature below which the resistance drops abruptly to zero. An electric current through a loop of superconducting wire can persist indefinitely with no power source.

Type-II superconductor

In superconductivity, a type-II superconductor is characterized by the formation of magnetic vortices in an applied magnetic field. This occurs above a certain critical field strength Hc1. The vortex density increases with increasing field strength. At a higher critical field Hc2, superconductivity is destroyed. Type-II superconductors do not exhibit a complete Meissner effect.

Titanium Chemical element with atomic number 22

Titanium is a chemical element with the symbol Ti and atomic number 22. It is a lustrous transition metal with a silver color, low density, and high strength. Titanium is resistant to corrosion in sea water, aqua regia, and chlorine.


Charles Hatchett identified the element columbium within a mineral discovered in Connecticut, US. Charles Hatchett.jpg
Charles Hatchett identified the element columbium within a mineral discovered in Connecticut, US.
Picture of a Hellenistic sculpture representing Niobe by Giorgio Sommer Sommer, Giorgio (1834-1914) - n. 2990 - Niobe madre - Firenze.jpg
Picture of a Hellenistic sculpture representing Niobe by Giorgio Sommer

Niobium was identified by English chemist Charles Hatchett in 1801. [4] [5] [6] He found a new element in a mineral sample that had been sent to England from Connecticut, United States in 1734 by John Winthrop F.R.S. (grandson of John Winthrop the Younger) and named the mineral columbite and the new element columbium after Columbia , the poetical name for the United States. [7] [8] [9] The columbium discovered by Hatchett was probably a mixture of the new element with tantalum. [7]

Connecticut U.S. state in the United States

Connecticut is the southernmost state in the New England region of the northeastern United States. As of the 2010 Census, it has the highest per-capita income, Human Development Index (0.962), and median household income in the United States. It is bordered by Rhode Island to the east, Massachusetts to the north, New York to the west, and Long Island Sound to the south. Its capital is Hartford and its most populous city is Bridgeport. It is part of New England, although portions of it are often grouped with New York and New Jersey as the tri-state area. The state is named for the Connecticut River which approximately bisects the state. The word "Connecticut" is derived from various anglicized spellings of an Algonquian word for "long tidal river".

John Winthrop the Younger Governor of the Saybrook and Connecticut Colonies

John Winthrop the Younger was an early governor of the Connecticut Colony, and he played a large role in the merger of several separate settlements into the unified colony.

Columbia (name) historical and poetic name used for the United States of America

Columbia is the personification of the United States. It was also a historical name used to describe the Americas and the New World. It has given rise to the names of many persons, places, objects, institutions and companies; for example: Columbia University, the District of Columbia, and the ship Columbia Rediviva, which would give its name to the Columbia River. Images of the Statue of Liberty largely displaced personified Columbia as the female symbol of the United States by around 1920, although Lady Liberty was seen as an aspect of Columbia. The District of Columbia is named after the personification, as is the traditional patriotic hymn "Hail Columbia", which is the official vice presidential anthem of the United States Vice President.

Subsequently, there was considerable confusion [10] 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 g/cm3, and tantalum—tantalite, with a density over 8 g/cm3, and concluded that the two oxides, despite the significant difference in density, were identical; thus he kept the name tantalum. [10] 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). [11] [12] This confusion arose from the minimal observed differences between tantalum and niobium. The claimed new elements pelopium, ilmenium , and dianium [13] were in fact identical to niobium or mixtures of niobium and tantalum. [14]

Tantalite tantalite mineral series

The mineral group tantalite [(Fe, Mn)Ta2O6] is the primary source of the chemical element tantalum. It is chemically similar to columbite, and the two are often grouped together as a semi-singular mineral called coltan or "columbite-tantalite" in many mineral guides. However, tantalite has a much greater specific gravity than columbite (8.0+ compared to columbite's 5.2). Iron-rich tantalite is the mineral tantalite-(Fe) or ferrotantalite and manganese-rich is tantalite-(Mn) or manganotantalite.

Tantalus Greek mythological figure, son of Zeus

Tantalus was a Greek mythological figure, most famous for his eternal punishment in Tartarus. He was also called Atys.

Niobe Greek mythological figure

In Greek mythology, Niobe was a daughter of Tantalus and of either Dione, the most frequently cited, or of Eurythemista or Euryanassa, and the sister of Pelops and Broteas.

The differences between tantalum and niobium were unequivocally demonstrated in 1864 by Christian Wilhelm Blomstrand [14] and Henri Etienne Sainte-Claire Deville, as well as Louis J. Troost, who determined the formulas of some of the compounds in 1865 [14] [15] and finally by Swiss chemist Jean Charles Galissard de Marignac [16] in 1866, who all proved that there were only two elements. Articles on ilmenium continued to appear until 1871. [17]

De Marignac was the first to prepare the metal in 1864, when he reduced niobium chloride by heating it in an atmosphere of hydrogen. [18] 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. [15] 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. [15] 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, [19] 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. [20] [21]

Naming the element

Columbium (symbol "Cb") [22] was the name originally bestowed by Hatchett upon his discovery of the metal in 1801. [5] The name reflected that the type specimen of the ore came from America (Columbia). [23] This name remained in use in American journals—the last paper published by American Chemical Society with columbium in its title dates from 1953 [24] —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. [25] 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. [25] This was a compromise of sorts; [25] 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". [26] [27] [28]



Niobium is a lustrous, grey, ductile, paramagnetic metal in group 5 of the periodic table (see table), with an electron configuration in the outermost shells atypical for group 5. (This can be observed in the neighborhood of ruthenium (44), rhodium (45), and palladium (46).)

Z Element No. of electrons/shell
23 vanadium 2, 8, 11, 2
41niobium2, 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. [29] Therefore, further research and discovery in this area is expected.

Niobium becomes a superconductor at cryogenic temperatures. At atmospheric pressure, it has the highest critical temperature of the elemental superconductors at 9.2  K. [30] Niobium has the greatest magnetic penetration depth of any element. [30] 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. [31]

When very pure, it is comparatively soft and ductile, but impurities make it harder. [32]

The metal has a low capture cross-section for thermal neutrons; [33] thus it is used in the nuclear industries where neutron transparent structures are desired. [34]


The metal takes on a bluish tinge when exposed to air at room temperature for extended periods. [35] Despite a high melting point in elemental form (2,468 °C), it has a lower density than other refractory metals. Furthermore, it is corrosion-resistant, exhibits superconductivity properties, and forms dielectric oxide layers.

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. [32] As a result, niobium's chemical properties are very similar to those for tantalum, which appears directly below niobium in the periodic table. [15] 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. [32]


Niobium in the Earth's crust comprises one stable isotope, 93Nb. [36] By 2003, at least 32 radioisotopes had been synthesized, ranging in atomic mass from 81 to 113. The most stable of these is 92Nb with a half-life of 34.7 million years. One of the least stable is 113Nb, with an estimated half-life of 30 milliseconds. Isotopes that are lighter than the stable 93Nb tend to decay by β+ decay, and those that are heavier tend to decay by β decay, with some exceptions. 81Nb, 82Nb, and 84Nb have minor β+ delayed proton emission decay paths, 91Nb decays by electron capture and positron emission, and 92Nb decays by both β+ and β decay. [36]

At least 25 nuclear isomers have been described, ranging in atomic mass from 84 to 104. Within this range, only 96Nb, 101Nb, and 103Nb do not have isomers. The most stable of niobium's isomers is 93mNb with a half-life of 16.13 years. The least stable isomer is 84mNb with a half-life of 103 ns. All of niobium's isomers decay by isomeric transition or beta decay except 92m1Nb, which has a minor electron capture branch. [36]


Niobium is estimated to be the 34th most common element in the Earth's crust, with 20  ppm. [37] Some think that the abundance on Earth is much greater, and that the element's high density has concentrated it in the Earth's core. [27] The free element is not found in nature, but niobium occurs in combination with other elements in minerals. [32] Minerals that contain niobium often also contain tantalum. Examples include columbite ((Fe,Mn)(Nb,Ta)2O6) and columbite–tantalite (or coltan, (Fe,Mn)(Ta,Nb)2O6). [38] Columbite–tantalite minerals (the most common species being columbite-(Fe) and tantalite-(Fe), where "-(Fe)" is the Levinson suffix informing about the prevailence of iron over other elements like manganese [39] [40] [41] [42] ) are most usually found as accessory minerals in pegmatite intrusions, and in alkaline intrusive rocks. Less common are the niobates of calcium, uranium, thorium and the rare earth elements. Examples of such niobates are pyrochlore ((Na,Ca)2Nb2O6(OH,F)) (now a group name, with a relatively common example being, e.g., fluorcalciopyrochlore [43] [44] [41] [42] [45] ) and euxenite (correctly named euxenite-(Y) [46] [41] [42] ) ((Y,Ca,Ce,U,Th)(Nb,Ta,Ti)2O6). These large deposits of niobium have been found associated with carbonatites (carbonate-silicate igneous rocks) and as a constituent of pyrochlore. [47]

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. [15] 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. [48] Together, those two mines produce about 88% of the world's supply. [49] 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. [49]

The third largest producer of niobium is the carbonatite-hosted Niobec mine, in Saint-Honoré, near Chicoutimi, Quebec, Canada, owned by Magris Resources. [50] It produces between 7% and 10% of the world's supply. [48] [49]


Niobium producers in 2006 to 2015 World Niobium Production 2006.svg
Niobium producers in 2006 to 2015

After the separation from the other minerals, the mixed oxides of tantalum Ta2O5 and niobium Nb2O5 are obtained. The first step in the processing is the reaction of the oxides with hydrofluoric acid: [38]

Ta2O5 + 14 HF → 2 H2[TaF7] + 5 H2O
Nb2O5 + 10 HF → 2 H2[NbOF5] + 3 H2O

The first industrial scale separation, developed by de Marignac, exploits the differing solubilities of the complex niobium and tantalum fluorides, dipotassium oxypentafluoroniobate monohydrate (K2[NbOF5]·H2O) and dipotassium heptafluorotantalate (K2[TaF7]) in water. Newer processes use the liquid extraction of the fluorides from aqueous solution by organic solvents like cyclohexanone. [38] 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: [51]

H2[NbOF5] + 2 KF → K2[NbOF5]↓ + 2 HF

Followed by:

2 H2[NbOF5] + 10 NH4OH → Nb2O5↓ + 10 NH4F + 7 H2O

Several methods are used for the reduction to metallic niobium. The electrolysis of a molten mixture of K2[NbOF5] 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, Nb2O5 is reduced with hydrogen or carbon. [51] In the aluminothermic reaction, a mixture of iron oxide and niobium oxide is reacted with aluminium:

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. [52] [53] Ferroniobium contains between 60 and 70% niobium. [48] 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. [54] [55]

As of 2013, CBMM from Brazil controlled 85 percent of the world's niobium production. [56] The United States Geological Survey estimates that the production increased from 38,700 tonnes in 2005 to 44,500 tonnes in 2006. [57] [58] Worldwide resources are estimated to be 4,400,000 tonnes. [58] During the ten-year period between 1995 and 2005, the production more than doubled, starting from 17,800 tonnes in 1995. [59] Between 2009 and 2011, production was stable at 63,000 tonnes per year, [60] with a slight decrease in 2012 to only 50,000 tonnes per year. [61]

Mine production (t) [62] (USGS estimate)
Flag of Australia (converted).svg  Australia 160230290230200200200???????
Flag of Brazil.svg  Brazil 30,00022,00026,00029,00029,90035,00040,00057,30058,00058,00058,00058,00045,00053,100
Flag of Canada (Pantone).svg  Canada 2,2903,2003,4103,2803,4003,3104,1673,0204,3804,3304,4204,6304,7105,260
Flag of the Democratic Republic of the Congo.svg  Congo D.R. ?5050135225????????
Flag of Mozambique.svg  Mozambique ??5341303429???????
Flag of Nigeria.svg  Nigeria 3530301901704035???????
Flag of Rwanda.svg  Rwanda 281207622636380???????
World 32,60025,60029,90032,80034,00038,70044,50060,40062,90062,90062,90063,00050,10059,400

Lesser amounts are found in Malawi's Kanyika Deposit (Kanyika mine).


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 and hydrogen at 200 °C; and with nitrogen at 400 °C, with products that are frequently interstitial and nonstoichiometric. [32] The metal begins to oxidize in air at 200 °C. [51] It resists corrosion by fused alkalis and by acids, including aqua regia, hydrochloric, sulfuric, nitric and phosphoric acids. [32] Niobium is attacked by hydrofluoric acid and hydrofluoric/nitric acid mixtures.

Although niobium exhibits all of the formal oxidation states from +5 to −1, the most common compounds have niobium in the +5 state. [32] Characteristically, compounds in oxidation states less than 5+ display Nb–Nb bonding. In aqueous solutions, niobium only exhibit 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. [54] Nb(V) is also slightly soluble in alkaline media due to the formation of soluble polyoxoniobate species. [63] [64]

Oxides and sulfides

Niobium forms oxides in the oxidation states +5 (Nb2O5), [65] +4 (NbO2), +3 (Nb
), [51] and the rarer oxidation state, +2 (NbO). [66] Most common is the pentoxide, precursor to almost all niobium compounds and alloys. [51] [67] Niobates are generated by dissolving the pentoxide in basic hydroxide solutions or by melting it in alkali metal oxides. Examples are lithium niobate (LiNbO3) and lanthanum niobate (LaNbO4). In the lithium niobate is a trigonally distorted perovskite-like structure, whereas the lanthanum niobate contains lone NbO3−
ions. [51] The layered niobium sulfide (NbS2) is also known. [32]

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 350 °C. [68] [69]


A sample of niobium pentachloride (yellow portion) that has partially hydrolyzed (white material). Niobium pentachloride solid.jpg
A sample of niobium pentachloride (yellow portion) that has partially hydrolyzed (white material).
Ball-and-stick model of niobium pentachloride, which exists as a dimer Niobium-pentachloride-from-xtal-3D-balls.png
Ball-and-stick model of niobium pentachloride, which exists as a dimer

Niobium forms halides in the oxidation states of +5 and +4 as well as diverse substoichiometric compounds. [51] [54] The pentahalides (NbX
) feature octahedral Nb centres. Niobium pentafluoride (NbF5) is a white solid with a melting point of 79.0 °C and niobium pentachloride (NbCl5) is yellow (see image at left) with a melting point of 203.4 °C. Both are hydrolyzed to give oxides and oxyhalides, such as NbOCl3. The pentachloride is a versatile reagent used to generate the organometallic compounds, such as niobocene dichloride ((C
). [70] The tetrahalides (NbX
) are dark-coloured polymers with Nb-Nb bonds; for example, the black hygroscopic niobium tetrafluoride (NbF4) and brown niobium tetrachloride (NbCl4).

Anionic halide compounds of niobium are well known, owing in part to the Lewis acidity of the pentahalides. The most important is [NbF7]2−, an intermediate in the separation of Nb and Ta from the ores. [38] This heptafluoride tends to form the oxopentafluoride more readily than does the tantalum compound. Other halide complexes include octahedral [NbCl6]:

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 [Nb6Cl18]4−. [71]

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. [72] The main niobium carbide is NbC, an extremely hard, refractory, ceramic material, commercially used in cutting tool bits.


A niobium foil Niobium metal.jpg
A niobium foil

Out of 44,500 tonnes of niobium mined in 2006, an estimated 90% was used in high-grade structural steel. The second largest application is superalloys. [73] Niobium alloy superconductors and electronic components account for a very small share of the world production. [73]

Steel production

Niobium is an effective microalloying element for steel, within which it forms niobium carbide and niobium nitride. [27] These compounds improve the grain refining, and retard recrystallization and precipitation hardening. These effects in turn increase the toughness, strength, formability, and weldability. [27] Within microalloyed stainless steels, the niobium content is a small (less than 0.1% [74] ) but important addition to high strength low alloy steels that are widely used structurally in modern automobiles. [27] 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. [75]

These same niobium alloys are often used in pipeline construction. [76] [77]


Apollo 15 CSM in lunar orbit with the dark rocket nozzle made from niobium-titanium alloy Apollo CSM lunar orbit.jpg
Apollo 15 CSM in lunar orbit with the dark rocket nozzle made from niobium-titanium alloy

Quantities of niobium are used in nickel-, cobalt-, and iron-based superalloys in proportions as great as 6.5% [74] for such applications as jet engine components, gas turbines, rocket subassemblies, turbo charger systems, heat resisting, and combustion equipment. Niobium precipitates a hardening γ''-phase within the grain structure of the superalloy. [78]

One example superalloy is 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. [79] [80] These superalloys were used, for example, in advanced air frame systems for the Gemini program. Another niobium alloy was used for the nozzle of the Apollo Service Module. Because niobium is oxidized at temperatures above 400 °C, a protective coating is necessary for these applications to prevent the alloy from becoming brittle. [81]

Niobium-based alloys

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 Nb-base 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 rocket thruster nozzles, such as the main engine of the Apollo Lunar Modules. [81]

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 niobium alloy. [82]

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" (possibly from columbium) that could be melted as buttons and rolled into sheet. Wah Chang 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 500-lb heat of C-103 in 1961, ingot to sheet, using EBM and VAR. The intended applications included turbine engines and liquid metal heat exchangers. Competing niobium alloys from that era included FS85 (Nb-10W-28Ta-1Zr) from 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. [81]

Superconducting magnets

A 3-tesla clinical magnetic resonance imaging scanner using niobium superconducting alloy Modern 3T MRI.JPG
A 3-tesla clinical magnetic resonance imaging scanner using niobium superconducting alloy

Niobium-germanium (Nb
), niobium-tin (Nb
), as well as the niobium-titanium alloys are used as a type II superconductor wire for superconducting magnets. [83] [84] These superconducting magnets are used in magnetic resonance imaging and nuclear magnetic resonance instruments as well as in particle accelerators. [85] For example, the Large Hadron Collider uses 600 tons of superconducting strands, while the International Thermonuclear Experimental Reactor uses an estimated 600 tonnes of Nb3Sn strands and 250 tonnes of NbTi strands. [86] In 1992 alone, more than US$1 billion worth of clinical magnetic resonance imaging systems were constructed with niobium-titanium wire. [20]

Other superconductors

A 1.3 GHz 9-cell SRF cavity made from niobium is on display at Fermilab A 1.3 GHz nine-cell superconducting radio frequency.JPG
A 1.3 GHz 9-cell SRF cavity made from niobium is on display at Fermilab

The superconducting radio frequency (SRF) cavities used in the free-electron lasers FLASH (result of the cancelled TESLA linear accelerator project) and XFEL are made from pure niobium. [87] A cryomodule team at Fermilab used the same SRF technology from the FLASH project to develop 1.3 GHz nine-cell SRF cavities made from pure niobium. The cavities will be used in the 30-kilometre (19 mi) linear particle accelerator of the International Linear Collider. [88] The same technology will be used in LCLS-II at SLAC National Accelerator Laboratory and PIP-II at Fermilab. [89]

The high sensitivity of superconducting niobium nitride bolometers make them an ideal detector for electromagnetic radiation in the THz frequency band. These detectors were tested at the Submillimeter Telescope, the South Pole Telescope, the Receiver Lab Telescope, and at APEX, and are now used in the HIFI instrument on board the Herschel Space Observatory. [90]

Other uses


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 ABO3 structure ferroelectrics like lithium tantalate and barium titanate. [91] Niobium capacitors are available as alternative to tantalum capacitors, [92] but tantalum capacitors still predominate. Niobium is added to glass to obtain a higher refractive index, making possible thinner and lighter corrective glasses.

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. [93] Niobium treated with sodium hydroxide forms a porous layer that aids osseointegration. [94]

Like titanium, tantalum, and aluminium, niobium can be heated and anodized ("reactive metal anodization") to produce a wide array of iridescent colours for jewelry, [95] [96] where its hypoallergenic property is highly desirable. [97]


A 150 Years Semmering Alpine Railway Coin made of niobium and silver 2004 Austria 25 Euro 150 Years Semmering Alpine Railway front.jpg
A 150 Years Semmering Alpine Railway Coin made of niobium and silver

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. [98] 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 €25 150 Years Semmering Alpine Railway commemorative coin, [99] and the 2006 Austrian €25 European Satellite Navigation commemorative coin. [100] The Austrian mint produced for Latvia a similar series of coins starting in 2004, [101] with one following in 2007. [102] In 2011, the Royal Canadian Mint started production of a $5 sterling silver and niobium coin named Hunter's Moon [103] in which the niobium was selectively oxidized, thus creating unique finishes where no two coins are exactly alike.


The arc-tube seals of high pressure sodium vapor lamps 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. [104] [105] [106]

Niobium is used in arc welding rods for some stabilized grades of stainless steel [107] and in anodes for cathodic protection systems on some water tanks, which are then usually plated with platinum. [108] [109]

Niobium is an important component of high-performance heterogeneous catalysts for the production of acrylic acid by selective oxidation of propane. [110] [111] [112] [113]

Niobium is used to make the high voltage wire of the Solar Corona particles receptor module of the Parker Solar Probe. [114]


GHS signal word Not listed as hazardous [115]
NFPA 704
Flammability code 0: Will not burn. E.g. waterHealth code 0: Exposure under fire conditions would offer no hazard beyond that of ordinary combustible material. E.g. sodium chlorideReactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no codeNiobium

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 frequently used in jewelry and has been tested for use in some medical implants. [116] [117]

Niobium-containing compounds are rarely encountered by most people, but some are toxic and should be treated with care. The short- and long-term exposure to niobates and niobium chloride, two chemicals that are water-soluble, have been tested in rats. Rats treated with a single injection of niobium pentachloride or niobates show a median lethal dose (LD50) between 10 and 100 mg/kg. [118] [119] [120] For oral administration the toxicity is lower; a study with rats yielded a LD50 after seven days of 940 mg/kg. [118]

Related Research Articles

Rhenium Chemical element with atomic number 75

Rhenium is a chemical element with the symbol Re and atomic number 75. It is a silvery-gray, heavy, third-row transition metal in group 7 of the periodic table. With an estimated average concentration of 1 part per billion (ppb), rhenium is one of the rarest elements in the Earth's crust. Rhenium has the third-highest melting point and highest boiling point of any stable element at 5903 K. Rhenium resembles manganese and technetium chemically and is mainly obtained as a by-product of the extraction and refinement of molybdenum and copper ores. Rhenium shows in its compounds a wide variety of oxidation states ranging from −1 to +7.

Tantalum Chemical element with atomic number 73

Tantalum is a chemical element with the symbol Ta and atomic number 73. Previously known as tantalium, its name comes from Tantalus, a villain from Greek mythology. Tantalum is a rare, hard, blue-gray, lustrous transition metal that is highly corrosion-resistant. It is part of the refractory metals group, which are widely used as minor components in alloys. The chemical inertness of tantalum makes it a valuable substance for laboratory equipment and a substitute for platinum. Its main use today is in tantalum capacitors in electronic equipment such as mobile phones, DVD players, video game systems and computers. Tantalum, always together with the chemically similar niobium, occurs in the mineral groups tantalite, columbite and coltan. Tantalum is considered a technology-critical element.

Columbite columbite series

Columbite, also called niobite, niobite-tantalite and columbate [(Fe, Mn)Nb2O6], is a black mineral group that is an ore of niobium. It has a submetallic luster and a high density and is a niobate of iron and manganese. This mineral group was first found in Haddam, Connecticut, in the United States. It forms a series with the tantalum-dominant analogue ferrotantalite and one with the manganese-dominant analogue manganocolumbite. The iron-rich member of the columbite group is ferrocolumbite. Some tin and tungsten may be present in the mineral. Yttrocolumbite is the yttrium-rich columbite with the formula (Y,U,Fe)(Nb,Ta)O4. It is a radioactive mineral found in Mozambique.

A period 5 element is one of the chemical elements in the fifth row of the periodic table of the elements. The periodic table is laid out in rows to illustrate recurring (periodic) trends in the chemical behaviour of the elements as their atomic number increases: a new row is begun when chemical behaviour begins to repeat, meaning that elements with similar behaviour fall into the same vertical columns. The fifth period contains 18 elements, beginning with rubidium and ending with xenon. As a rule, period 5 elements fill their 5s shells first, then their 4d, and 5p shells, in that order; however, there are exceptions, such as rhodium.

Group 5 element group of chemical elements

Group 5 is a group of elements in the periodic table. Group 5 contains vanadium (V), niobium (Nb), tantalum (Ta) and dubnium (Db). This group lies in the d-block of the periodic table. The group itself has not acquired a trivial name; it belongs to the broader grouping of the transition metals.

Manganese oxide is any of a variety of manganese oxides and hydroxides. These include

Superalloy Alloy with higher durability than normal metals

A superalloy, or high-performance alloy, is an alloy that exhibits several key characteristics: excellent mechanical strength, resistance to thermal creep deformation, good surface stability, and resistance to corrosion or oxidation. The crystal structure is typically face-centered cubic austenitic. Examples of such alloys are Hastelloy, Inconel, Waspaloy, Rene alloys, Incoloy, MP98T, TMS alloys, and CMSX single crystal alloys.

Pelopium was the proposed name for a new element found by the chemist Heinrich Rose in 1845. The name derived from the Greek king and later god Pelops, son of Tantalus. During the analysis of the mineral tantalite he concluded that it does contain an element similar to niobium and tantalum. The similar reactivity of niobium and tantalum complicated preparation of pure samples and therefore several new elements were proposed, which were later found to be mixtures of niobium and tantalum.

Lithium niobate chemical compound

Lithium niobate (LiNbO3) is a compound of niobium, lithium, and oxygen. Its single crystals are an important material for optical waveguides, mobile phones, piezoelectric sensors, optical modulators and various other linear and non-linear optical applications. It is a human-made dielectric material that does not exist in nature. Lithium niobate is sometimes referred to by the brand name linobate.

Tantalum pentoxide chemical compound

Tantalum pentoxide, also known as tantalum(V) oxide, is the inorganic compound with the formula Ta
. It is a white solid that is insoluble in all solvents but is attacked by strong bases and hydrofluoric acid. Ta
is an inert material with a high refractive index and low absorption, which makes it useful for coatings. It is also extensively used in the production of capacitors, due to its high dielectric constant.

Niobium pentoxide chemical compound

Niobium pentoxide is the inorganic compound with the formula Nb2O5. It is a colourless insoluble solid that is fairly unreactive. It is the main precursor to all materials made of niobium, the dominant application being alloys, but other specialized applications include capacitors, lithium niobate, and optical glasses.

Burundi is a producer of columbium (niobium) and tantalum ore, tin ore, and tungsten ore, and some deposits of gold which are designated for export. Burundi has resources of copper, cobalt, nickel, feldspar, phosphate rock, quartzite, and rare reserves of uranium, and vanadium. The country is also a producer of limestone, peat, sand and gravel for domestic consumption and as building materials. As of 2005, manufacturing accounted for 8% of the country's gross domestic product.

Dianium was the proposed name for a new element found by the mineralogist and poet Wolfgang Franz von Kobell in 1860. The name derived from the Roman goddess Diana. During the analysis of the mineral tantalite and niobite he concluded that it does contain an element similar to niobium and tantalum. The symbol was Di.

A niobium alloy is one in which the most common element is niobium.

Potassium heptafluorotantalate chemical compound

Potassium heptafluorotantalate is an inorganic compound with the formula K2[TaF7]. It is the potassium salt of the heptafluorotantalate anion [TaF7]2−. This white, water-soluble solid is an intermediate in the purification of tantalum from its ores and is the precursor to the metal.

Ixiolite an oxide mineral with the consisting of tantalum (Ta), niobium (Nb) and tin (Sn) and often found in granitic pegmatites.

Ixiolite is an accessory oxide mineral found in granitic pegmatites. It is an oxide with the general chemical formula (Ta,Nb,Sn,Mn,Fe)4O8 or (Ta,Mn,Nb)O2.


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