Piezoelectric and Ultrasonic Studies of Mixed CuInP₂(S_XSe_{1 - X})₆Layered Crystals

Abstract

Results of ultrasonic and piezoelectric properties investigation of mixed CuInP 2 (S X Se 1−X ) 6 layered ferroelectric single crystals are presented. The piezoelectric detection of longitudinal ultrasonic signal by thin plates of CuInP 2 (S x Se 1−x ) 6 crystals (x=0.05, 0.1, 0.2 and 0.25) was observed and the temperature dependencies of piezoelectric properties have been studied. The piezoelectric sensitivity decreased upon heating and vanished at higher temperature, where crystals exhibit phase transition (PT) to centrosymmetric phase. At transition temperatures the anomalies of ultrasonic velocity and attenuation have been observed. At room temperature, above PT, the electrostrictioninduced piezoelectricity was observed under DC bias electric field applied along c-axis of the CuInP 2 (S x Se 1−x ) 6 crystals.

Phase Transitions in Layered Semiconductor - Ferroelectrics

“…Ultrasonic investigations were performed by automatic computer controlled pulse-echo method and the main results are presented in papers (Samulionis et al, 2007;Samulionis et al, 2009a;Samulionis et al, 2009b). Usually in CuInP 2 S 6 family crystals ultrasonic measurements were carried out using longitudinal mode in direction of polar c-axis across layers.…”

Stress-induced phase transitions in nanoscale CuInP2S6

“…1). The elastic compliances 𝑠 𝑖𝑗 were estimated from the ultrasound velocity measurements [34,36,48]. These parameters are summarized in Table I.…”

“…The CuInP2(S,Se)6 family reveals very unusual features of a nonlinear dielectric response indicating that a spontaneous polarization may exist above the transition temperature [32], extremely large elastic nonlinearity in the direction perpendicular to the layers [33,34], a giant negative electrostriction and dielectric tunability [35], the electrostriction induced piezoelectricity above the ferroelectric transition temperature [36], morphotropic phase transitions between its monoclinic and trigonal phases [37], and anomalous "bright" domain walls with enhanced local piezoelectric response [38,39].…”