Niobium, Nb (Formerly Columbium, Cb) - Properties, Applications

Topics Covered

Chemical Properties
Physical Properties
Mechanical Properties
Thermal Properties


Niobium is a white, ductile metal that shows a light bluish tinge after prolonged exposure to air at room temperatures. It was originally named as columbium by Charles Hatchett who discovered it in 1801. In order to put an end to the confusion due to the difference in the naming of this element in different countries, IUPAC officially named it Niobium. The atomic number of niobium is 41 and it belongs to the d-block, period 5 of the periodic table. The chemical symbol of niobium is Nb.

Niobium starts to oxidize in air when subjected to high temperatures; hence the handling of the metal under high temperatures needs to be done under a protective environment to minimize oxidation. Columbite, samarskite and betafite are the ores of niobium. The main geographical areas where columbite is mined are Brazil, Russia, Nigeria and Canada.

The physical and chemical properties of niobium are similar to tantalum. Apart from reacting with oxygen in air at high temperatures, niobium is reactive to carbon, nitrogen, sulfur and halogens. Niobium is non-reactive to acids and moisture at room temperatures but reacts with acids at elevated temperatures. Niobium and its compounds may cause irritation to eyes and skin.

This datasheet will look into the properties and applications of niobium.

Chemical Properties

The chemical properties of niobium are provided in the table below:

Chemical Data
CAS number 7440-03-1
Thermal neutron cross section 1.1 barns/atom
Ionic radius 0.7 Å
Electro negativity 1.6
Electrochemical equivalent 0.0693 g/A/h

Physical Properties

The following table discusses the physical properties of niobium.

Properties Metric Imperial
Density 8.4 g/cm3 0.303 lb/in3
Melting point 2410 °C 4370 °F
Boiling point 5100 °C 9212°F

Mechanical Properties

The mechanical properties of niobium are tabulated below.

Properties Metric Imperial
Tensile strength (at room temperature) 275 MPa 40 ksi
Modulus of elasticity 105 GPa 15250 ksi
Shear modulus 38 GPa 5511 ksi
Poissons Ratio 0.4 0.4
Hardness, Brinell 736 736
Hardness, Vickers 1320 1320
Hardness, Mohs 6 6

Thermal Properties

The thermal properties of niobium are tabulated below.

Properties Metric Imperial
Thermal expansion co-efficient (@20-100°C/68-212°F) 7.3 µm/m°C 4 µin/in°F
Thermal conductivity 53.7 W/mK 1133 BTU in/hr.ft².°F


The following are the application areas of niobium:

  • Production of high-temperature resistant alloys and special stainless steel
  • Optics
  • Superconductors
  • Super alloys.

Niobium compounds such as niobium carbide are used in cutting tools. Other compounds such as lithium niobate are used in electroceramics. Niobium-tin alloys are used as superconducting magnets. Niobium is used in stainless steel alloys that are used in nuclear reactors, missiles, jets, pipelines, cutting tools and welding rods.

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