Microstructure and piezoelectric properties of (1-x)(Na0.5K0.5)NbO3-xLiNbO3 ceramics

(1-x)(Na0.5K0.5)NbO3-xLiNbO(3) [(1-x)NKN-xLN] ceramics were produced by the conventional solid-state sintering method, and their microstructure and piezoelectric properties were investigated. The formation of the liquid phase and K6Li4Nb10O30 second phase that were observed in the (1-x)NKN-xLN ceramics was explained by the evaporation of Na2O during the sintering. A morphotropic phase boundary (MPB) was observed in the specimens with 0.05 < x < 0.08. Promising piezoelectric properties were obtained for the specimens with x = 0.07. Therefore, the piezoelectric properties of this 0.93NKN-0.07LN ceramic were further investigated and were found to be influenced by their relative density and grain size. In particular, grain size considerably affected the d(33) value. Two-step sintering was conducted at different temperatures to increase the grain size. Piezoelectric properties of d(33) = 240 (pC/N) and k(p) = 0.35 were obtained for the 0.93NKN-0.07LN ceramics sintered at 1030 degrees C and subsequently annealed at 1050 degrees C.