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)O-3 (BCTZ.x) 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 degrees C in a reducing atmosphere of pO(2) = 5 x 10(2) 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 T-1 was shifted to 36 degrees C near room temperature for Zr content of x = 4 at.%. The piezoelectric constant d(33), electromechanical coupling coefficient k(p), and dielectric constant epsilon(r) 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)O-3 ceramics, which are promising as a lead-free piezoelectric candidate. (C) 2010 Elsevier B.V. All rights reserved.