Intermediate phases in rhombohedral Pb(Mg1/3Nb2/3)1-xTixO3 crystal

Abstract

Phase transformations of (111)-cut Pb(Mg1∕3Nb2∕3)1−xTixO3 (x=0.30) single crystals before and after an electric (E)–field poling have been investigated by means of dielectricpermittivity, hysteresis loop, polarization current, and in situx-ray diffraction as a function of temperature. An R-T-C transition sequence was observed in the unpoled sample upon zero-field heating. R, T, and C are rhombohedral, tetragonal, and cubic phases, respectively. After a prior E-field poling, an extra intermediate monoclinic (possible MA) phase was induced and the crystal underwent an R-MA-T-C phase sequence with significant responses in polarization current. The dielectric dispersion was diminished after poling and reappeared in the cubic state. The dielectricpermittivities with and without a prior poling were found to follow the Curie–Weiss equation, ε′=C/(T−T0), above the Burns temperature 505K with the same constants C=1.9×105 K and T0=460K.