Effect of La concentration on the kinetics of the induced phase transition in PbMg$_{1/3}$Nb$_{2/3}$O$_{3}$–25PbTiO$_{3}$ transparent ceramics

The effect of La concentration on the kinetic nature of the induced phase transition in PbMg$_{1/3}$Nb$_{2/3}$O$_{3}$–25PbTiO$_{3}$ ferroceramics was studied. At temperatures below the Vogel–Fulcher temperature, the time-dependent changes in the dielectric constant and optical transmission in electric fields are studied 0 $<E<6$ kV/cm. It was found that in an electric field in La-containing transparent ceramics, a sharp decrease in the dielectric constant and optical transmission occurs over time, indicating an induced phase transition and an increase in the fraction of the ferroelectric phase. It has been shown that in undoped La ceramics the changes in the dielectric constant at the same fields are much smaller. It was found that the stability of the induced phase depends on the La concentration: the higher the concentration, the lower the stability. The results obtained are explained by both a varying degree of diffuse of the phase transition and different sizes of polar regions, which depend on the La concentration.