Physical Properties of Niobium

Atomic number41
Atomic mass92.91 [g/mol]
Melting point2468 [°C]
Boiling point4927 [°C]
Atomic volume1.80 • 10-29 [m3]
Vapour pressureat 1800 °C (2073 K)7 • 10-6 [Pa]
at 2500 °C (2773 K)2 • 10-1 [Pa]
Density at 20 °C8.56 [g/cm3]
Lattice structurebody-centred-cubic
Lattice constant329.4 • 10-12 [m]
Hardness at 20 °Ccold-worked110 - 180 [HV10]
recrystallized60 - 110 [HV10]
Young's modulus at 20 °C104 [GPa]
Poisson's ratio0.35
Linear coefficient of thermal expansion at 20 °C7.1 • 10-6 [m/(m•K)]
Thermal conductivity at 20 °C52 [W/(m•K)]
Specific heat at 20 °C0.27 [J/(g•K)]
Electrical conductivity at 20 °C7 • 10-6 [1/(Ω•m)]
Specifi c electrical resistance at 20 °C0.14 [(Ω•mm2)/m]
Acoustic velocity at 20 °C
longitudinal wave4920 [m/s]
transverse wave2100 [m/s]
Electron work function4.36 [eV]
Thermal neutron capture cross section1.15•10-28 [m2]
Recrystallization temperature(1 hour at temp)850 - 1300 [°C]
Superconductivity (transition temperature)< 9.2 [K]

Chemical Properties of Niobium

Niobium is a lustrous, grey, ductile, paramagnetic metal in group 5 of the periodic table, although it has an atypical configuration in its outermost electron shells compared to the rest of the members.

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. These properties— especially the superconductivity —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 atoms of niobium is slightly less electropositive and smaller than the atoms of its predecessor in the periodic table, zirconium, while it is virtually identical in size to the heavier tantalum atoms which are subject to the lanthanide contraction. As a result, niobium's chemical properties are very similar to the chemical properties of 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 exact uses such as linings in chemical plants.