Intrinsic polarization switching in BaTiO3 crystal under uniaxial electromechanical loading

Both ${180}^{\ensuremath{\circ}}$ and ${90}^{\ensuremath{\circ}}$ intrinsic polarization switching (IPS) in $\mathrm{BaTi}{\mathrm{O}}₃$ crystal were investigated by Landau-Ginzburg-Devonshire (LGD) theory under combined electric field and stress loading. Results show that for ${180}^{\ensuremath{\circ}}\phantom{\rule{0.16em}{0ex}}\mathrm{PS}$, the coercive electric field $({E}_IC^{{180}^{\ensuremath{\circ}}})$ increases under tension but decreases under compression with increasing stresses. The ${90}^{\ensuremath{\circ}}\phantom{\rule{0.16em}{0ex}}\mathrm{PS}$ was classified into two types. For type I ${90}^{\ensuremath{\circ}}\phantom{\rule{0.16em}{0ex}}\mathrm{PS}, {E}_IC^{\mathrm{I}\phantom{\rule{0.28em}{0ex}}({90}^{\ensuremath{\circ}})}$ increases under tension but decreases under compression with increasing stresses, similar to ${180}^{\ensuremath{\circ}}\phantom{\rule{0.16em}{0ex}}\mathrm{PS}$; while for type II ${90}^{\ensuremath{\circ}}\phantom{\rule{0.16em}{0ex}}\mathrm{PS}$, an opposite variation trend is observed. (The definition of the type I and the type II ${90}^{\ensuremath{\circ}}\phantom{\rule{0.16em}{0ex}}\mathrm{PS}$ is given in the text.) Additionally, the calculation demonstrates that under tensile stresses or under compressive stresses between \ensuremath{-}140 and 0 MPa, the electric field needed to drive both types of ${90}^{\ensuremath{\circ}}\phantom{\rule{0.16em}{0ex}}\mathrm{PS}$ is smaller than that needed for driving ${180}^{\ensuremath{\circ}}\phantom{\rule{0.16em}{0ex}}\mathrm{PS}$, implying that ${180}^{\ensuremath{\circ}}\phantom{\rule{0.16em}{0ex}}\mathrm{PS}$ is favorable to accomplish by two-step ${90}^{\ensuremath{\circ}}\phantom{\rule{0.16em}{0ex}}\mathrm{PS}$. As ${E}_IC$ refers to ${180}^{\ensuremath{\circ}}\phantom{\rule{0.16em}{0ex}}\mathrm{PS}$ in the past investigations, these demonstrate that the ${E}_IC$ calculated by others may be overestimated. Moreover, the coercive stresses needed to drive ${90}^{\ensuremath{\circ}}$ ferroelastic IPS was also calculated as a function of preloading bias electric fields.