Electric field-induced dynamics of structural ordering in ternary PbIn$_{1/2}$Nb$_{1/2}$O$_{3}$–PbMg$_{1/3}$Nb$_{2/3}$O$_{3}$–$x$PbTiO$_{3}$ systems

The electric field-induced dynamics of the phase transition to a ferroelectric phase in PbIn$_{1/2}$Nb$_{1/2}$O$_{3}$–PbMg$_{1/3}$Nb$_{2/3}$O$_{3}$–$x$PbTiO$_{3}$ ($x$ = 25 and 32%) crystals have been studied in different geometries of applying an external electric field $E\parallel$ [001] and $E\parallel$ [011]. The optical transmission, the sound velocity, and the sound damping have been measured simultaneously at room temperature. It was found that the change in the elastic properties follows the change in the optical transmission, which is related to different polar region sizes and relaxation times, to which light and sound are responsive. It was found that, in the field range 0–2 kV/cm at $E\parallel$ [001], both the crystals demonstrate only a partial polarization as a result of the phase transition, while the phase transition in the PT32 crystal at $E\parallel$ [011] is finished by almost complete polarization of the sample in the same field range.