With the atomic number of 73, tantalum (Ta) is a member of the refractory group of metals. It is a hard blue-grey lustrous metal and very inert, making it a good substitute for the more expensive platinum. It is often found co-existing with niobium in minerals such as coltan, columbite and tantalite.
Tantalum was discovered in 1802 in Sweden by Anders Ekeberg who noted its great anti-corrosion properties. The main industrial source of tantalum is in Australia.
Despite being an inert element, tantalum is a good conductor of electricity and heat. It is hard and highly resistant against corrosion by acid with one of the highest boiling points of any metal – at 3017°C.
Interestingly, tantalum exists in two forms: alpha and beta. In its alpha form, it is soft and deforms easily, while it becomes more fragile and hard in its beta phase.
Isolating tantalum means separating it from its sister element niobium. This begins with leaching through the use of acid to form hydrogen fluorides, which are removed using solvents. Since niobium needs a higher level of acidity to remain solvent, it’s then relatively easier to separate the two elements.
Tantalum is a highly important resource for the electrical component industries, where it is used in the manufacture of capacitors. Due to its high melting point, it is also used in the production of alloys for high temperature applications. Due to tantalum’s inert properties, it is also ideal for surgical implants. Its heat resistant properties make it a popular component in:
- Jet engines
Tantalum’s name comes from the character, Tantalus, from Greek mythology, a man who was condemned to stand in water to his knees with fruit hanging from a tree just above him. Unfortunately, he could reach neither to drink nor eat. Its discoverer, Ekeberg, named the element due to its incapability to be absorbed or saturated by acid.
|Melting point||2 996 °C / 3 269 K|
|Boiling point||6 100 °C / 6 373 K|
|Atomic volume||1.80 · 10-29 [m3]|
|Vapor pressure||at 1 800 °C||5 · 10-8 [Pa]|
|at 2 200 °C||7 · 10-5 [Pa]|
|Density at 20 °C||16.60 [g/cm3]|
|Crystal structure||body-centred cubic|
|Lattice constant||3.303 · 10-10 [m]|
|Hardness at 20 °C||deformed||120 – 220 [HV10]|
|recrystallized||80 – 125 [HV10]|
|Modulus of elasticity 20 °C||186 [GPa]|
|Coefficient of linear thermal expansion at 20 °C||6.4 · 10-6 [m/(m·K)]|
|Thermal conductivity at 20 °C||54 [W/(m·K)]|
|Specific heat at 20 °C||0.14 [J/(g·K)]|
|Electrical conductivity at 20 °C||8 · 10-6 [1/(Ω·m)]|
|Specific electrical resistance at 20 °C||0.13 [(Ω·mm2)/m]|
|Sound speed at 20 °C||Longitudinal wave||4 100 [m/s]|
|Transverse wave||2 900 [m/s]|
|Electron work function||4.3 [eV]|
|Capture cross-section for thermal neutrons||2.13 · 10-27 [m2]|
|Recrystallization temperature (annealing time: 1 hour)||900 – 1 450 °C|
|Superconductive (transition temperature)||< -268.65 °C / < 4.5 K|