Barium hexaboride is a hard material with a high melting point. It can be formed by passing a barium vapour at >750 ðC over boron crystals:
However, it can also be formed by reacting barium chloride with boron in two stages: firstly at 900 ðC for 30 minutes and then at 1,500 ðC for 60 minutes.
Barium hexaboride has been considered as a candidate for use in hot-cathode electron guns.