Low-Temperature Synthesis of Calcium Hexaboride Powder via Transient Boron Carbide Formation

Calcium hexaboride (CaB6) powder was synthesized by carbothermal reduction using a low‐temperature synthesis method for boron carbide (B4C) powder. A B4C precursor consisting of boron oxide (B2O3) and carbon components was prepared from a condensed boric acid (H3BO3)‐poly(vinyl alcohol) (PVA) product by thermal decomposition in air, which was then mixed with calcium carbonate (CaCO3) powder. CaB6 was formed via the transient formation of calcium borate (Ca3B2O6) and B4C, which were in close contact owing to the finely dispersed B2O3/carbon structure of the B4C precursor. CaB6 powder with fine particles was synthesized by heat treatment at 1400°C for 10 h in an Ar flow.