Microstructural analyses of B4C–CeO2 and B4C–La2O3 ceramics

Abstract Effects of additions of CeO 2 and La 2 O 3 on microstructure and mechanical properties of B 4 C fabricated under and without hot press have been investigated. Vickers hardness and fracture strength are increased by hot press due to the reduction of porosity because the sintering rate is enhanced. Hardness is increased by the reduction of porosity because crack probably occurs when the hardness is measured due to pore as an initiation point of crack. Hardness increases with increasing additions of CeO 2 and La 2 O 3 because porosity decreases due to the formation of CeB 6 and LaB 6 on the grain boundary of B 4 C, respectively. The borides are formed through reaction between solid phases, which might induce coherent boundary between boride and B 4 C. Such coherency also contributes to strengthening the grain boundary of B 4 C. The addition of CeO 2 enhances the sintering rate more than that of La 2 O 3 , resulting in higher hardness of B 4 C–CeO 2 than that of B 4 C–La 2 O 3 .