Dielectric, hypersonic, and domain anomalies of (PbMg1/3Nb2/3O3)1-x(PbTiO3)x single crystals

Abstract

Dielectricpermittivities,Brillouinbackscattering spectra, polarization-electric field hysteresis loops, and domain structures have been measured as a function of temperature in relaxor-based ferroelectricsingle crystals(PbMg1/3Nb2/3O3)1−x(PbTiO3)x(PMN-xPT)(PbMg1/3Nb2/3O3)1−x(PbTiO3)x(PMN-xPT) for x=0.24x=0.24 and 0.34. For PMN-24%PT, a diffuse phase transition which is associated with a broad frequency-dependent dielectric maximum was observed near 380 K. As the temperature increases, the PMN-24%PT crystal gradually develops cubic regions and is fully converted into the cubic state near 375 K. An extra dielectric anomaly appears at 370 K, possibly due to the percolating polar cluster induced by an external electric field. PMN-34%PT exhibits a nearly normal ferroelectric phase transition near 445 K from the tetragonal to the cubic phase. In addition, a weak diffuse phase transition observed near 280 K may result from partial conversion of rhombohedral phase to tetragonal phase. The dielectric thermal hysteresis confirms that the transitions near 280 and 445 K are diffuse first order and first order, respectively. The dielectricpermittivities of PMN-24%PT and PMN-34%PT obey the relation, ε′m/ε′(f,T)=1+[T−Tm(f )]γ/2δ2γ,εm′/ε′(f,T)=1+[T−Tm(f )]γ/2δγ2, above the temperature of permittivity maximum Tm.