Size-dependent properties in Ba0.85Ca0.15Ti0.90Zr0.10O3-based ceramics

Ba0.85Ca0.15Ti0.90Zr0.10O3 (BCTZ) pseudobinary ferroelectric is one of the most promising BT-based materials for piezoelectric applications. In this work, a series of dense BCTZ ceramics with grain size larger than 1?m and uniform grain-size distribution were successfully prepared by the conventional solid-state reaction, and the grain-size effects on the structural, dielectric, ferroelectric and piezoelectric properties were explored in their un-poled and poled states. The ceramics were obtained by sintering solid state powders at different temperatures between 1400- 1500°C and times (from 0.2-24 hours). The grain size of ceramics determined from SEM images were between 2 ?m for the samples sintered at 1400ºC/2h to 27 ?m for the samples obtained at 1500ºC /24h. The structural characterization was performed for monitoring the effect of grain size and field on the phase composition in BCTZ ceramics. The evolution of polar order and phase transitions with grain size has been studied using dielectric permittivity measurements at 20Hz- 2MHz between 25 and 150°C. Also, the piezoelectric properties at different poling conditions (poling temperature and electric field) were investigated and discussed according with ceramics grain size. Polarization vs. electric field (P-E) hysteresis loop study showed that exist a critical grain size (~ 9 ?m) for which the remnant and saturation polarisation is higher. The same critical size was obtained from dc-tunability investigation. In addition, we develop a mesoscale modelling (Monte Carlo with Finite Element Method calculations) to describe size effects on the low-field properties in BCTZ ceramics. The presented data provide a complete picture of the size effect dependence of functional properties in Ba0.85Ca0.15Ti0.90Zr0.10O3 ceramics. Acknowledgements: The financial support of the PN III-P1-1.1-TE-2016-1951 is acknowledged