Microstructure and toughening mechanisms in An Al₂O₃ ceramic matrix composite dispersed with LiTaO₃ particles

LiTaO₃ (5-25vol%) dispersed Al₂O₃ matrix composite (LTA) with high relative density were fabricated by hot pressing at 1300°C. The microstructure and mechanical properties of the composite were studied. The main results are as follows: Al₂O₃ was found to be phase compatible with piezoelectric LiTaO₃ during high temperature sintering process. The relative density of the LTA composites was greatly improved by the addition of LiTaO₃ particles. Domains are clearly discerned in LiTaO₃ grains in the LTA composite, confirming that LiTaO₃ particles remain ferroelectrics. 90 degree domains were observed in LiTaO₃ grains constrained strongly by Al ₂O₃ matrix, which has never been found in LiTaO ₃ single crystal before. Comparing with those of pure Al ₂O₃, sintered at same temperature (1300°C), both the flexural strength and the fracture toughness of the composites are all enhanced. Domain switching is suggested as a new toughening mechanism in the ferroelectric particles dispersed structural ceramics.