Investigations on phase coexistence and functional properties of BCZT lead-free piezoceramic

Abstract

Large piezoelectric properties was observed in (1-x)BZT-(x)BCT where x=0.5 or Ba0.85Ca0.15Ti0.9Zr0.1O3 (denoted as BCZT), leading to a promising candidate for lead-free piezoelectric materials. However, phase formation of the BCZT is controversial and still unclear since various phase coexistences were identified in the literatures, for instances, the mixed phases of rhombohedral-tetragonal (R-T), ortho-rhombic-tetragonal (O-T) or rhombohedral-orthorhombic-tetragonal (R-O-T). Additionally, it is well known that the crystal structure plays a crucial role on the occurrence of polarization in the piezoceramics. Therefore, this work aims to investigate the coexistence of phase formation at room temperature for the BCZT powder and ceramic. Moreover, the electrical properties as a function of temperature, frequency and electric field were observed in order to evaluate the extrinsic contribution of piezoelectric response. It was found that, according to the results from temperature-dependent dielectric properties as well as Rietveld refinement of XRD profiles, the coexistence of O-T phase was observed in the BCZT powder and ceramic. Furthermore, the enhancement of Ca2+ substitution into Ba2+ site in BCZT ceramic caused the shrinkage of unit cell, leading to the shift of XRD profile and Raman spectra. In addition, it was found that the applications of frequency and electric field can influence on changes of domain-wall motion and micro-polar cluster in the BCZT piezoceramic.