Mechanism behind piezoelectricity and thermal expansion behaviour of BaTiO3-based lead-free ceramics with various strontium dopants

Abstract

Sr-doped BaTiO₃ piezoelectric ceramics have attracted considerable interest for potential applications in electronic components owing to their excellent electrical properties. In this study, Ba_0.95-xSr_xCa_0.05Ti_0.9Zr_0.1O₃ (BSCTZ) lead-free ceramics were synthesised by conventional solid-state sintering at 1190 °C with as-prepared BSCTZ nanoparticles. La dopants were selected to reduce the number of oxygen vacancies during the preparation process, and MnO₂ and CuO were introduced to reduce the sintering temperature. Changes in the phase, fracture morphology, dielectricity, ferroelectricity, and piezoelectricity with increasing x were examined. Our results show that Sr promotes orthorhombic-to-tetragonal phase evolution, decreases the average grain size, improves dielectric relaxation, increases ferroelectric diffuseness, and enhances the piezoelectricity of BSCTZ ceramics. With increasingly excessive strontium content, the ferroelectricity and piezoelectricity decreased, and the domain-switching activation energy increased. These changes are attributable to disturbed long-range dipoles, large compositional fluctuations, and fine grains. Optimal electrical properties were observed when the strontium content was 0.12. The Born–Lande theory was used to investigate the mechanism of thermal expansion behaviour. The study results provide a valuable reference for research on multifunctional BaTiO₃-based piezoelectric ceramics modified with Sr.