Preparation of CaB6 powder via calciothermic reduction of boron carbide

The method of calciothermic reduction of B 4 C was proposed for preparing CaB 6 . The phase transition and morphology evolution during the reaction were investigated in detail. The experimental results reveal that Ca first reacts with B 4 C to generate CaB 2 C 2 and CaB 6 at a low temperature and that the CaB 2 C 2 subsequently reacts with Ca to produce CaB 6 and CaC 2 at a high temperature. After the products were leached to remove the byproduct CaC 2 , pure CaB 6 was obtained. The grain size of the prepared CaB 6 was 2–3 μm, whereas its particle size was 4–13 μm; it inherited the particle size of B4C. The residual C content of the product was decreased to 1.03wt% after the first reaction at 1173 K for 4 h and the second reaction at 1623 K for 4 h.