The electroacoustic effect in a strontium titanate single crystal under a structural phase transition

Results of an experimental study of the special features of the electroacoustic effect in a strontium titanate single crystal in the region of a structural phase transition at $T\approx103$ К are presented. The propagation speed of longitudinal ultrasonic waves at a frequency 30 MHz as a function of the external electric field E is measured. As the temperature decreases and approaches $T\approx103$ K, the functional dependence of the sound speed on the electric field strength is observed to gradually change from quadratic to linear. The emergence of a linear contribution to the transition region is related to the defect-induced deviation of the lattice symmetry from the cubic one.