Improving piezoelectric property of BaTiO3–CaTiO3–BaZrO3 lead-free ceramics by doping

Abstract

1wt% Li2CO3- or La2O3-doped 0.75BaTiO3–0.15CaTiO3–0.1BaZrO3 (BCZT) lead-free ceramics were prepared by the solid-state reaction method sintered at 1480–1520°C for 2h. Sintering temperature, oxide doping and poling electric field influence crystal structure and electrical properties of the sintered BCZT ceramics. Due to oxide doping the BCZT ceramics exhibit pure perovskite structure sintered in a rather wide sintering temperatures with composition locating at the rhombohedral side around the morphotropic phase boundary. The oxide-doped BCZT ceramics exhibit rather homogeneous microstructure morphology, in which grain size of the Li2CO3-doped BCZT ceramics and La2O3-doped BCZT ceramics is around nm-scale and in μm-scale, respectively. Li2CO3 doping increases the value of dielectric constant maximum (εm), sharpens the dielectric response peaks and suppresses the dielectric frequency dispersion of the BCZT ceramics, whereas the temperature of εm (TC/Tm) changes negligibly. As comparison, La2O3 doping decreases the Tm temperature and enhances dielectric frequency dispersion greatly. The Li2CO3-doped BCZT ceramics exhibit similar P–E hysteresis loop to that of the undoped BCZT ceramics, whereas La2O3 doping deteriorates ferroelectric property apparently. Li2CO3 doping improves piezoelectric property whereas La2O3 doping deteriorates piezoelectric property of the BCZT ceramics, which can be interpreted by the formation of different point-charge defects induced by oxide doping.