Induced phase transition in monocrystalline solids solutions PbMg$_{1/3}$Nb$_{2/3}$O$_{3}$–29PbTiO$_{3}$ and PbZn$_{1/3}$Nb$_{2/3}$O$_{3}$–9PbTiO$_{3}$: similarity and difference

The kinetics of the induced phase transition in single-crystal relaxor solid solutions PbMg$_{1/3}$Nb$_{2/3}$O$_{3}$–29PbTiO$_{3}$ and PbZn$_{1/3}$Nb$_{2/3}$O$_{3}$–9PbTiO$_{3}$ is studied when an electric field is applied along the [001] direction. At temperatures below the temperature of the morphotropic phase transition, the changes in the dielectric constant and optical transmission in electric fields are studied. It is shown that the decrease in optical transmission with time is associated only with a change in the sizes of nanoregions during the phase transition. It was found that the induced phase transition proceeds differently in these crystals. In PMN-29PT crystals, the formation of ferroelectric phases and the rapid establishment of macroscopic polarization are preceded by a certain delay time, while in PZN-9PT crystals, the ferroelectric phase is induced immediately after the application of the field without a delay time. The results obtained are explained by the different structures of the low-temperature phases in these compounds.