Microstructure and Piezoelectric Properties of (1− x )(Na 0.5 K 0.5 )NbO 3 – x LiNbO 3 Ceramics

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(1− x )(Na 0.5 K 0.5 )NbO 3 – x LiNbO 3 [(1− x )NKN– x LN] 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 K 6 Li 4 Nb 10 O 30 second phase that were observed in the (1− x )NKN– x LN ceramics was explained by the evaporation of Na 2 O 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°C and subsequently annealed at 1050°C.