Evidence of local anisotropic strains in relaxor ferroelectrics below intermediate temperature T* detected by acoustic emission

Oriented {100}-, {110}-, and {111}-cuts of Pb(0.78)Ba(0.22)Sc(0.5)Ta(0.5)O(3) single crystals have been studied by means of the acoustic emission (AE) method during their thermal cycling in the temperature range of 300-600 K. For all crystal orientations pronounced AE signals have been detected near 490 K, which corresponds to the intermediate temperature T*. However, the highest AE count rate has been detected from {110}-oriented cuts, revealing strong anisotropic coupling between the existing polar species that at T* merge into larger regions of polarization (PNRs). The temperature's hysteresis is revealed to be 15 K, indicating that the transformation processes at T* can be considered as local Martensitic-like ferroelectric transitions inside PNRs. The interplay between PNRs and ultrahigh local strains of perovskite-type relaxor ferroelectrics is discussed.