Optical and acoustic properties of 33PbIn$_{1/2}$Nb$_{1/2}$O$_3$–35PbMg$_{1/3}$Nb$_{2/3}$O$_3$–32PbTiO$_3$ single crystals in an electric field

The influence of different conditions of applying a dc electric field (0 $< E <$ 4 kV/cm) on the behavior of optical transmission and on the acoustic parameters (sound velocity and attenuation) in the [001]- and [011]-oriented single crystals 33PbIn$_{1/2}$Nb$_{1/2}$O$_3$–35PbMg$_{1/3}$Nb$_{2/3}$O$_3$–32PbTiO$_3$ existing near the morphotropic phase boundary has been investigated. It has been found that the optical transmission, sound velocity, and attenuation sharply change near the phase transition in a narrow range of electric fields for any method of their applying. In the field applied along [001], the change in the sound velocity due to the phase transition is 1.5 times greater than that in the field applied along [011]. This is caused by a larger contribution of the piezoelectric effect to the elastic modulus determining the sound velocity along [001] as compared to [011]. It has been shown that the number, symmetry, and stability of the phases formed in the field depend on the conditions of applying the field.