Effect of sintering process on microstructure of Al2O3/LiTaO3 composite ceramics

Effects of different sintering methods such as pressureless sintering and hot press sintering on relative density and microstructure of the Al2O3P/LiTaO3 (ALT) composite ceramics were investigated to obtain a preferable sintering process. Relative densities of all ALT composites are below 90% when sintered with the cold isostatical pressing followed by pressureless sintering at temperatures of 1250 to 1350 degrees C. The relative densities and microstructure of ALT composite ceramics with the hot press sintering process in a N-2 atmosphere at 1150 and 1300 degrees C were investigated. The relative density of ALT composite hot pressed at 1150 degrees C is only 77%, and almost theoretical density at 1300 degrees C. This indicates that sintering pressure plays an important role in the densification of ALT composite ceramics in temperature range of 1150 to 1350 degrees C. Investigation on morphologies of the composites shows that the Al2O3 particles distributed along grain boundaries of LiTaO3, which leads to a fine-grained microstructure in the ALT composite ceramics.