Phase-transition behavior and piezoelectric properties of lead-free (Ba0.95Ca0.05)(Ti1−xZrx)O3 ceramics

We report the enhancement of piezoelectric properties of (Ba0.95Ca0.05)(Ti1−xZrx)O3 (BCTZx) ceramics by optimizing Zr content in the range of 0 ≤ x ≤ 15 at.%. The BCTZx were synthesized by the solid-state reaction method and sintered at 1350 °C in a reducing atmosphere of pO2 = 5 × 102 Pa, for potential co-firing with base metal electrodes (BMEs). The BCTZx ceramics were characterized by an orthorhombic to pseudocubic polymorphic phase transition (PPT) at 5 ≤ x ≤ 7 at.%, based on X-ray diffraction patterns. The orthorhombic to pseudocubic phase-transition temperature T1 was shifted to 36 °C near room temperature for Zr content of x = 4 at.%. The piezoelectric constant d33, electromechanical coupling coefficient kp, and dielectric constant ɛr were optimized to 338 pC/N, 36%, and 2070, respectively. The results indicate that optimizing Zr content is an effective way to enhance the piezoelectric properties of (Ba,Ca)(Ti,Zr)O3 ceramics, which are promising as a lead-free piezoelectric candidate.