Synthesis of substitutional hexaboride of lanthanum and cerium La1–xCexB6 via aluminothermic reduction

Rare-earth hexaborides (REB 6 ) are vital raw materials for cathode materials and high temperature structural ceramics that are widely applied as high-frequency electron tubes and ceramics adaptive for extreme environment, respectively. In this work, single phase substitutional solid solution REB 6 (LaB 6 , La 0.75 Ce 0.25 B 6 , La 0.5 Ce 0.5 B 6 , La 0.25 Ce 0.75 B 6 and CeB 6 ) powders were prepared with the raw materials of La 2 O 3 , CeO 2 , B 4 C and Al powders, after calcining at 1773 K for 4 h and the following alkaline leaching. All substitutional solid solution products have homogeneous distributions of La and Ce in particles. Through microscopic morphology analysis, it is discovered that the formation of solid solution is beneficial for reducing the particle size of product, relative to LaB 6 and CeB 6 . Moreover, Al flux plays an important role in decarbonizing reaction, and C contents of all products are below 0.4 wt%.