Large electrostrain near the phase transition temperature of (Bi0.5Na0.5)TiO3–SrTiO3 ferroelectric ceramics

Abstract

$\left(1\text{-}x\right)\left({\mathrm{Bi}}_{0.5}{\mathrm{Na}}_{0.5}\right)\mathrm{Ti}{\mathrm{O}}_3–x\mathrm{Sr}\mathrm{Ti}{\mathrm{O}}_3$ (abbreviated as $\mathrm{BNST}100x$ ) was prepared by a conventional ceramic fabrication process. The depolarization temperature $T_d$ , rhombohedral-tetragonal phase transition temperature $T_{R\text{-}T}$ , and the temperature $T_m$ of the maximum dielectric constant were determined from the temperature dependence of the dielectric and piezoelectric properties. It is revealed that $\mathrm{BNST}100x$ forms a morphotropic phase boundary of rhombohedral ferroelectric and pseudocubic (tetragonal) paraelectric at $x=0.26–0.28$ for $\mathrm{BNST}100x$ , and a very large strain and normalized strain $d_{33}{}^{*}$ of 0.29% and $488\mathrm{pm}∕\mathrm{V}$ , respectively, were obtained at $x=0.28$ . In addition, it was clarified that the intermediate phase between $T_{R\text{-}T}$ $(⩾T_d)$ and $T_m$ shows relaxor behavior.