Microstructure and mechanical properties of a lithium tantalate-dispersed-alumina ceramic composite

Ceramic composites with a ferroelectric/piezoelectric secondary phase were studied. Lithium tantalate (LiTaO3) was found to be phase compatible with alumina (Al2O3) during sintering. LiTaO3/Al2O3 ceramic composites were fabricated by two processing routes. The microstructure and mechanical properties of the ceramic composites were investigated comparatively. Domain structures were clearly seen in LiTaO3, confirming that LiTaO3 remained ferroelectric. σf and KIC reached 438.7 MPa and 5.4 MPa·m1/2, respectively, for 5 vol.%LiTaO3/Al2O3 ceramic composite prepared by cold isostatically pressing and pressureless sintering in air at 1300 °C followed by hot isostatically pressing at 1300 °C, where energy dissipation due to domain switching or/and the piezoelectric effect is suggested as a new toughening mechanism in structural ceramic. The toughening effect is counteracted for higher concentrations of such ferroelectric/piezoelectric secondary phase due to the decreased relative density.