Hysteretic phase transition sequence in0.67Pb(Mg1/3Nb2/

Domain pattern variations with temperature were studied by polarizing light microscopy for the morphotropic phase boundary composition $0.67\mathrm{Pb}(\mathrm{M}{\mathrm{g}}_{1/3}\mathrm{N}{\mathrm{b}}_{2/3}){\mathrm{O}}_{3}\ensuremath{-}0.33\mathrm{PbTi}{\mathrm{O}}_{3}$ (PMN-0.33PT) single crystal. At room temperature, the monoclinic ${\mathrm{M}}_{\mathrm{A}}$ phase is the dominant phase in the unpoled crystal, which coexists with a small fraction of the tetragonal (T) phase. The orientation of spontaneous polarization was calculated to be $\ensuremath{\sim}4.{8}^{\ensuremath{\circ}}$ away from the pseudocubic ${\ensuremath{\langle}111\ensuremath{\rangle}}_{C}$ in the ${{001}}_{C}$ plane family. Under an electric field of 6 kV/cm along ${[011]}_{C}$, a single domain orthorhombic (O) phase was induced but partially switched back to ${\mathrm{M}}_{\mathrm{A}}$ a few hours after the removal of the $E$ field. It was found that the temperature induced phase transition sequence of the ${[011]}_{C}$ poled PMN-0.33PT single crystal is strongly hysteretic. On heating, the phase transition sequence is as follows: coexistence of O phase and ${\mathrm{M}}_{\mathrm{A}}\ensuremath{\rightarrow}\mathrm{rhombohedral}\ensuremath{\rightarrow}\mathrm{monoclinic}\phantom{\rule{0.16em}{0ex}}{\mathrm{M}}_{\mathrm{C}}\ensuremath{\rightarrow}\mathrm{cubic}\phantom{\rule{0.16em}{0ex}}(\mathrm{C})$. On cooling, the phase transition sequence is given by $\mathrm{C}\ensuremath{\rightarrow}\mathrm{T}\ensuremath{\rightarrow}{\mathrm{M}}_{\mathrm{A}}$. The complete set of dielectric, piezoelectric, and elastic constants for the ${[011]}_{C}$ poled PMN-0.33PT single crystal was measured, which showed the strong feature of the single domain O phase with high shear $({d}_{15}=2321\phantom{\rule{0.16em}{0ex}}\mathrm{pC}/\mathrm{N},\phantom{\rule{0.16em}{0ex}}{d}_{24}=1941\phantom{\rule{0.16em}{0ex}}\mathrm{pC}/\mathrm{N})$ and low longitudinal piezoelectric coefficients $({d}_{33}=165\phantom{\rule{0.16em}{0ex}}\mathrm{pC}/\mathrm{N})$.