Ultrasonic and piezoelectric studies of new layered ferroelectric compounds of Sn 2P 2S 6 family

Abstract

Ultrasonic and piezoelectric studies of two-dimensional layered crystalline structures of MM 1P 2X 6 (M,M 1 = Cu, In, Sn, Cr; X = S, Se) are presented in this contribution. It was shown, that such materials: CuInP 2S 6, CuCrP 2S 6 and CuInP 2Se 6 undergo phase transitions (PT) and exhibit piezoelectric effect in low temperature phases. Anomalies of ultrasonic velocity and attenuation at phase transitions have been observed in these materials. Measurements of temperature dependencies of ultrasonic velocity and attenuation revealed the first order phase transition at T c ≈ 312 K in CuInP 2S 6; two successive phase transitions at T c1 ≈ 180 K and T c2 ≈ 145 K in CuCrP 2S 6; and two phase transitions at T c1 ≈ 235 K and T c2 ≈ 228 K in CuInP 2Se 6.