40-60nm

Purity:99.9%

Characteristics

Physical

Niobium is a lustrous, grey, ductile, paramagnetic metal in group 5 of the periodic table (see table), although it has an atypical configuration in its outermost electron shells compared to the rest of the members. (This can be observed in the neighborhood of ruthenium , rhodium , and palladium .

Niobium becomes a superconductor at cryogenic temperatures. At atmospheric pressure, it has the highest critical temperature of the elemental superconductors: 9.2 K. Niobium has the largest magnetic penetration depth of any element. In addition, it is one of the three elementalType II superconductors, along with vanadium and technetium. The superconductive properties are strongly dependent on the purity of the niobium metal. When very pure, it is comparatively soft and ductile, but impurities make it harder.

The metal has a low capture cross-section for thermal neutrons; thus it is used in the nuclear industries.

Chemical

The metal takes on a bluish tinge when exposed to air at room temperature for extended periods. Despite presenting a high melting point in elemental form (2,468 °C), it has a low density in comparison to 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, owing to thelanthanide contraction. As a result, niobium's chemical properties are very similar to those for tantalum, which appears directly below niobium in the periodic table. Although its corrosion resistance is not as outstanding as that of tantalum, its lower price and greater availability make niobium attractive for less demanding uses such as linings in chemical plants.

Isotopes

Naturally occurring niobium is composed of one stable isotope, ⁹³Nb. By 2003, at least 32 radioisotopes had been synthesized, ranging in atomic mass from 81 to 113. The most stable of these is⁹²Nb 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 andpositron emission, and ⁹²Nb decays by both β⁺ and β⁻ decay.

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 decay chain.

Occurrence

Niobium is estimated to be the 33rd most common element in the Earth’s crust, with 20 ppm.Some think that the abundance on Earth is much greater, but that the "missing" niobium may be located in the Earth’s core due to the metal's high density. The free element is not found in nature, but niobium occurs in combination with other elements in minerals. Minerals that contain niobium often also contain tantalum. Examples include columbite ((Fe,Mn)(Nb,Ta)₂O₆) andcolumbite–tantalite (or coltan, (Fe,Mn)(Ta,Nb)₂O₆). Columbite–tantalite minerals 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)) and euxenite ((Y,Ca,Ce,U,Th)(Nb,Ta,Ti)₂O₆). These large deposits of niobium have been found associated with carbonatites (carbonate-silicateigneous rocks) and as a constituent of pyrochlore.

The two largest deposits of pyrochlore were found in the 1950s in Brazil and Canada, and both countries are still the major producers of niobium mineral concentrates. The largest deposit is hosted within a carbonatite intrusion atAraxá, Minas Gerais Brazil, owned by CBMM (Companhia Brasileira de Metalurgia e Mineração); the other deposit is located in Goiás and owned by Anglo American plc (through its subsidiary Mineração Catalão), also hosted within a carbonatite intrusion. Altogether these two Brazilian mines produce around 75% of world supply. The third largest producer of niobium is the carbonatite-hosted Niobec Mine, Saint-Honoré near Chicoutimi, Quebec owned by Iamgold Corporation Ltd, which produces around 7% of world supply. Kenya's deposits found in Kwale are ranked amongst the top six in the world. Recently, NioCorp has considered opening a mine in Elk Creek, Nebraska to begin domestic production in the United States.