Structure-microstructure-property relationships in lead-free BCTZ piezoceramics processed by conventional sintering and spark plasma sintering

Lead-free piezoelectric ceramics belonging to the pseudo-binary system (1 − x)BaTi0.8Zr0.2O3-x Ba0.7Ca0.3TiO3(BCTZ, x = 0.32 and 0.5) were prepared using conventional sintering and spark plasma sintering. This comparative study shows how the macroscopic properties of ferroelectric BCTZ perovskites are affected when the grain size is decreased. The crystallographic structure and the microstructural characteristics are thoroughly investigated for ceramic samples obtained by both sintering methods. We clearly demonstrate that the dielectric, piezoelectric, pyroelectric and ferroelectric properties in SPS ceramics are strongly affected by the grain size and the structural defects leading to local strain fields which undermine the polarisation flexibility. This confirms that the critical compositions showing remarkably large piezoelectric coefficients are extremely sensitive to external and internal stresses.