Effects of CaTiO3 addition on microstructures and electrical properties of Na0.52K0.48NbO3 lead-free piezoelectric ceramics

In this article, various amounts of CaTiO3 (CT) were added into (Na0.52K0.48)NbO3 (NKN) ceramics using conventional oxide-mixing method for improving NKN's properties. The experimental results show that the (1−x)(Na0.52K0.48)NbO3–xCaTiO3 (x=0∼0.07) solid solution system can be successfully synthesized. Addition of CaTiO3 not only effectively prevents materials from deliquescence, but also improves the density and the electrical properties of the ceramics. The dielectric constant–temperature (εr−T) curves exhibit that the temperatures of the Curie point (Tc) and the phase transition from tetragonal to orthorhombic (TO−T) are decreasing monotonously as the amount of CT addition is increased. A morphotropic phase boundary (MPB) can be found in the (1−x)NKN−xCT solid solution system as the doping amount of x=0.03, and the 0.97NKN–0.03CT ceramics, with a high bulk density, 98% theoretical density, and an appropriate grain size of about 1∼2μm, present a superior domain switching ability and the optimum properties: d33=117pC/N, kp=0.39, Pr=21μC/cm2, and Tc=333°C.