Preparation and electrical properties of pseudoternary BaTiO 3 –CaTiO 3 –BaZrO 3 lead free piezoelectric ceramics

Abstract

Pseudoternary xBaTiO₃–yCaTiO₃–(1−x−y)BaZrO₃ (BT–CT–BZ) lead free piezoelectric ceramics were prepared by the conventional solid state reaction method sintered at 1450–1510°C for 2 h. Sintering conditions, composition and polarisation conditions exert great influences on structure and electrical properties of the sintered BT–CT–BZ ceramics. The synthesised BT–CT–BZ ceramics exhibit rather large bulk density and densified microstructure morphology, although slight content of pyrochlore phase impurity exists. With increasing CaTiO₃ content, crystal structure of the BT–CT–BZ ceramics changes gradually from rhombohedral perovskite structure, across morphotropic phase boundary (MPB) composition and to tetragonal one. The dielectric response character changes successively from broad dielectric peaks to narrow ones accompanied by slight content of dielectric frequency dispersion, whereas the MPB effect is not apparent. The temperature of dielectric constant maximum T_C increases almost linearly with increasing CaTiO₃ content. The BT–CT–BZ ceramics exhibit fully developed, saturated and symmetric polarisation–electric field P–E hysteresis loops, excellent piezoelectric property and perfect electromechanical resonance response peaks, in which the MPB effects are detected clearly by ferroelectric and piezoelectric properties measurements.