Kinetic features of the new phase nucleation in the electric field in some lead-containing relaxors

The kinetics and dynamics of the new phase nucleation in an external electric field E in ferroelectric relaxors PbIn$_{1/2}$Nb$_{1/2}$O$_{3}$–PbMg$_{1/3}$ Nb$_{2/3}$O$_{3-x}$PbTiO$_{3}$ ($x$ = 25 и 32%) and PbMg$_{1/3}$Nb$_{2/3}$O$_{3}$–29PbTiO$_{3}$. have been investigated. The joint measurements of optical transmittance at different wavelengths as well as the sound speed and attenuation at different frequencies have been carried out at room temperature. The analysis of the character of the changes of the optical and acoustic properties in different electric fields has been performed with the aim of identifying the mechanisms of such changes under phase transition conditions. The reduction of optical transmission with time is associated only with the size change of nanoregions in the process of phase transition. The observed acoustic anomalies are the consequence of phase transition and conditioned by the lattice increased rigidity, caused by a large piezoelectric effect in the ferroelectric phase.