Tantalum and niobium
 

Tantalum and niobium are metals belonging to the 5th group of transition elements in the periodic tables. Tantalum was discovered in 1804, niobium in 1844. The name 'tantalum' was chosen by the discoverer A.G. Ekeberg because the oxide Ta205 does not react and form salts with acids and therefore it "cannot quench its thirst - just like Tantalus in the Underworld". Niobium, which occurs naturally in combination with tantalum, gets its name from Tantalus' daughter, Niobe.

When they occur naturally tantalum and niobium are generally found in the form of the mineral iron tantalate (Fe, Mn) (TaO3)2 and iron niobate (Fe, Mn) (NbO3)2 - and always together. By dissolving them with elementary chlorine, followed by fractional distillation of the volatile chloride and subsequent reduction using a strong reduction agent such as sodium metal - the two metals can be separated forming the respective metal sponges. Consolidation is effected either by conductive sintering or remelting in an electron beam furnace.

Both tantalum and niobium have a body-centered lattice cubic structure yielding high levels of strength and ductility. They form extremely stable oxides making them comparable with precious metals in their corrosion resistance. They are used as a construction material in chemical equipment involving highly corrosive applications and as alloying elements in the production of steel and stainless steel. Additionally, tantalum is used as a material for implants and surgical instruments and in electronics (tantalum capacitors).

Properties of tantalum and niobium