Phases and Domain Structures in Relaxor-Based Ferroelectric (PbMg1/3Nb2/3O3)0.69(PbTiO3)0.31 Single Crystal

Abstract

The Brillouin back-scattering spectra, dielectric permittivities, polarization–electric field (P–E) hysteresis loops and domain structures have been measured as a function of temperature in a relaxor-based ferroelectric single crystal (PbMg1/3Nb2/3O3)0.69(PbTiO3)0.31 (PMN–31%PT). In order of increasing temperature, PMN–31%PT undergoes successive phase transitions: rhombohedral phase (below ∼370 K) →coexistence of rhombohedral and tetragonal phases (between ∼370 and ∼380 K) →tetragonal phase (between ∼380 and ∼400 K) →coexistence of tetragonal and cubic phases (betwee ∼400 and ∼420 K) →cubic phase (above ∼420 K). An extra ferroelectric anomaly of the dielectric permittivity appears at 370 K possibly due to the percolating polar cluster induced by an external electric field. It was found that different individual domain regions have different transition temperatures. This phenomenon suggests an inhomogeneous distribution of Ti4+ concentration in the PMN–31%PT crystal. The dielectric permittivity ε′ of PMN–31%PT obeys the empirical relation, ε′m/εγ(f,T)=1+[T-Tm(f)]′/2δγ2, above the temperature of permittivity maximum Tm.