Effect of Electrical Field on the Phase Transformation of 0.7Pb(Mg1/3Nb2/3)O-3-0.3PbTiO(3) Single Crystals

The structural phase transformations of 0.7Pb(Mg1/3Nb2/3)O-3-0.3PbTiO(3) (PMN-0.3PT) were studied using high resolution x-ray diffraction (HRXRD) as a function of temperature and electric field. A phase transformational sequence of cubic (C) -> tetragonal (T) -> rhombohedral (R) phase was observed in zero-field-cooled conditions; and a C -> T -> monoclinic (MC) -> monoclinic (M-A) phase was observed in the field-cooled conditions. The transformation of T to M-A phase was realized through an intermediate M-C phase. The results also represent conclusive and direct evidence of a M-C to M-A phase transformation in field-cooled conditions. Beginning from the zero-field-cooled condition, a R -> M-A -> M-C -> T phase transformational sequence was found with an increasing electric field at a fixed temperature. Upon removal of the field, the M-A phase was stable at room temperature. With increasing the field, the transformation temperature from T to M-C and from M-C to M-A phase decreased, and the phase stability ranges of both T and M-C phases increased. Upon removal of the field, the phase transformation from R to M-A phase was irreversible, but from M-A to M-C was reversible, which means that M-A is the dominant phase under the electric field. In the M phase region, the results confirmed that lattice parameters and tilt angles were weakly temperature dependent over the range of investigated temperatures.