Interfacial reaction behavior and thermal stability of barium zirconate-coated alumina fiber/alumina matrix composites

A barium zirconate (BaZrO3) coating was incorporated onto surfaces of alumina fibers, and the coated alumina fiber/alumina matrix composites were prepared by hot pressing. The interfacial reactions between BaZrO3 coating and Al2O3 fiber/matrix during the consolidation resulted in formation of ZrO2 and Ba–β-Al2O3, one of nonstoichiometric hexaluminate compounds. The diffusion of Ba cations dominates the reaction process between BaZrO3 coating and Al2O3 fiber/matrix. The Ba–β-Al2O3 phase exhibited an elongated morphology due to preferred orientational growth through directional diffusion and mass transport of Ba along the basal plane. The Young's modulus and hardness of the Ba–β-Al2O3 phase were measured by nanoindentation technique to be 250 GPa and 20 GPa, respectively. The BaZrO3-coated Al2O3 fiber/Al2O3 matrix composites showed good microstructural stability during thermal exposure up to 1400 °C.