Characterization of lead-based relaxor ferroelectric crystals by acoustic emission

The acoustic emission (AE) method is presented as a useful complementary tool for nondestructive characterization of selective relaxor ferroelectrics. Combined measurements of the dielectric permittivity and AE activity as a function of temperature and externally applied electric fields have been carried out using Pb(Mg_1/3Nb_2/3)O₃–33%PbTiO₃ (PMN-0.33PT) single crystals and Pb(Sc_0.5Ta_0.5)O₃ (PST) single crystals. Anomalous behavior in the electric field dependencies of the characteristic temperatures, T_m (diffuse permittivity maximum in PMN-PT) and T_n (formation of incommensurate antiferroelectric domains in PST), and the associated AE intensities has been observed. Both T_m and T_n exhibit minima coinciding with the AE activities maxima at critical values of the applied dc electric fields, 0.5 and 0.13 kV respectively. These phenomena are discussed mainly in terms of the interaction of the external field with the random electric fields originating from the polar nanoregions in relaxor ferroelectrics.