Phase transformation above Tm in PbSc0.5Ta0.5O3 relaxor as seen via acoustic emission

Chemically B-site disordered PbSc1/2Ta1/2O3 relaxor crystals have been studied by means of dielectric and acoustic emission methods in the vicinity of T-m approximate to 280 K. Along with the intrinsic cubic-to-rhombohedral phase transformation at T-c = 261 K, a phase transformation at T-n = 293 K is evidently detected by acoustic emission. Under an external dc electric field T-c gradually increases with increasing the field, whereas T-n exhibits nontrivial behavior, namely, initially decreases and then starts increasing, similarly to T-c. The characteristic temperature T-n is attributed to the occurrence of incommensurate modulated antiferroelectric regions, which have previously been suggested to coexist with both the cubic paraelectric and rhombohedral ferroelectric phases in the vicinity of T-m. The nontrivial behavior of T-n under an external dc electric field is also discussed.