Preparation and mechanical properties of LaNbO₄-MoSi₂ ceramic composites

LaNbO₄ powder was synthesized by high-temperature solid phase reaction,and LaNbO₄-MoSi₂ ceramic composites were synthesized by hot pressing in this paper.The microstructures and fracture characteristics were analyzed by scanning electron microscope,metallographic microscope and X ray diffractometer.And the microhardness,bend strength and fracture toughness were tested at the same time.The experimental results showed that there were still some remaining La₂O₃ which had not been reacted in the synthesized LaNbO₄ powder,and the high energy ball-milling of raw powder before solid phase reaction made the structure of LaNbO₄ change from monoclinic to mainly tetragonal state.Compared with MoSi₂ sample,the crystal grain of LaNbO₄-MoSi₂ composite sample was obviously fine,and the compactness was increased.Microhardness,bend strength and fracture toughness were greatly improved as well.It is valuable to investigate MoSi₂ matrix ceramics reinforced with LaNbO₄ particles as a new composite phase,which has a characterization of domain structure transfer.