High piezoelectric d33 coefficient in (Ba1 − xCax)(Ti0.98Zr0.02)O3 lead-free ceramics with relative high Curie temperature

Lead-free (Ba_1 − xCa_x)(Ti_0.98Zr_0.02)O₃ (x = 0-0.04) ceramics were prepared successfully using a solid-state reaction technique. The polymorphic phase transitions (PPT) from orthorhombic to tetragonal phase around room temperature were identified in the composition range of 0 < x < 0.03. High piezoelectric coefficient of d₃₃ = 375 pC/N and planar electromechanical coupling factor of k_p = 44.1% were obtained for the samples at x = 0.01. With the increase of Ca content, the orthorhombic-tetragonal phase transitions shifted towards room temperature, while relative high Curie temperature (T_C) was still maintained about 115 °C.