Transformation of the physical properties of PbIn$_{1/2}$Nb$_{1/2}$O$_3$–PbMg$_{1/3}$Nb$_{2/3}$O$_3$–PbTiO$_3$ crystals in an electric field

The influence of the composition and different modes of applying a direct-current (dc) electric field (0 $< E <$ 4 kV/cm) on the behavior of the temperature dependences of the dielectric permittivity, optical transmission, as well as the velocity and attenuation of sound, has been investigated in the [001]-oriented PbIn$_{1/2}$Nb$_{1/2}$O$_3$–PbMg$_{1/3}$Nb$_{2/3}$O$_3$–PbTiO$_3$ single crystals located both far from the morphotropic phase boundary and in its vicinity. It has been found that, in the phase transition region in a narrow field range for any mode of applying an electric field, all the crystals under investigation are characterized by abrupt changes in their physical properties. It has been shown that the phase transition rate and the attenuation of sound are different in the crystals located at different distances from the morphotropic phase boundary. The $E$–$T$ phase diagrams have been constructed for different modes of applying an electric field. It has been demonstrated that the phase diagrams constructed for the same crystal but different modes of applying an electric field differ from each other. Possible reasons for the observed phenomena have been discussed.