The dielectric and piezoelectric pr

The dielectric and piezoelectric properties of KNN ceramics prepared by CSAS and CS methods are shown in Fig. 8. As shown in Fig. 8(a), benefiting from high density and stable sintering behavior, KNN ceramics produced by CSAS possess high d33 values in the sintering temperature range. The sintering temperature for CSAS samples can lower down to 1055°C to maintain a practicable d33 value of 105pC/N, whereas only 65pC/N for CS samples sintered at the same temperature. The trend of piezoelectric coefficient with the rising sintering temperature is very similar to the density profile in Fig. 4, except the fact that the maximum value of d33 was obtained at 1115°C, a little bit lower the temperature where the highest density was achieved. This phenomenon must be relative to the different volatilization degree of K and Na, which results from the severe evaporation of KNbO3 when the heating temperature exceeds its melting point[37]. Meanwhile, the value of d33 for CSAS produced ceramics decreased only 3% (from 131 to 127pC/N) when the environmental temperature increased from 25℃ to 230℃ (show in Fig. 8(b)), which means they are very stable in a large scale of operation temperature range.