Texture-based ferroelectric hardening in Na1/2Bi1/2TiO3 -based piezoceramics

Abstract

${\mathrm{Na}}_{1/2}{\mathrm{Bi}}_{1/2}\mathrm{Ti}{\mathrm{O}}_{3}$-based (NBT-based) ceramics offer a viable option to replace lead-based materials for high-power applications as they are characterized by a stable mechanical quality factor with increasing vibration velocity in comparison to lead-based piezoceramics. Recently, the minor and stable extrinsic contributions were revealed as the origin for the stability of the mechanical quality factor with increasing vibration velocity. This work identifies the very unusual high poling degree as cause for the small extrinsic contributions. To this end, complete pole figure densities have been quantified and correlated to the piezoelectric coefficient and electromechanical quality factor. This hypothesis is further strengthened by correlating the piezoelectric constant (sum of intrinsic and extrinsic contributions) with the remanent polarization (correlates to remanent texturing degree). In order to assess a full picture of NBT-based piezoceramics, $0.94{\mathrm{Na}}_{1/2}{\mathrm{Bi}}_{1/2}\mathrm{Ti}{\mathrm{O}}_{3}\text{\ensuremath{-}}0.06\mathrm{BaTi}{\mathrm{O}}_{3}$ has been considered with and without Zn doping and with quenching. It is compared to $0.79{\mathrm{Na}}_{1/2}{\mathrm{Bi}}_{1/2}\mathrm{Ti}{\mathrm{O}}_{3}\text{\ensuremath{-}}0.21\phantom{\rule{0.16em}{0ex}}{\mathrm{K}}_{1/2}{\mathrm{Bi}}_{1/2}\mathrm{Ti}{\mathrm{O}}_{3}$ with and without Mg doping. Finally, a contrast to soft $\mathrm{Pb}({\mathrm{Zr}}_{1/2}{\mathrm{Ti}}_{1/2}){\mathrm{O}}_{3}$ (PZT) flushes out the impact of domain wall motion on the piezoelectric coefficient and the electromechanical quality factor. Whereas a PZT-based reference material exhibits a linear increase in the piezoelectric constant with increasing remanent polarization, the NBT-based materials deviate from the linear trend, indicating a decrease in extrinsic contributions.