Electrical Properties of K0.5Na0.5NbO3 Lead-free Piezoceramics by Pressureless Sintering

Lead-free piezoceramics K0.5Na0.5NbO3 were prepared by pressureless sintering. The effects of sintering temperature on the density and electrical properties of KNN ceramics were investigated. The results show that the density of the KNN ceramics changes dramatically in a narrow temperature range of 1065-1120 degrees C. The density of the ceramic sintered at 1100 degrees C reaches 4.35 g/cm(3) (95% of the theoretical density). The ceramic sintered at 1100 degrees C shows the best electrical properties: the maximum piezoelectric coefficient of about 118 pC/N, the maximum relative dielectric constant of 538, the minimum dielectric loss of 4.70%, the remanent polarization of 15.37 mu C/cm(2) and the coercive electric field of 13.16 kV/cm. The phase transformation temperature from orthorhombic to tetragonal is about 206 degrees C, and the Curie temperature is 410 degrees C.