The structural phase transformations of 0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 (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 (MA) phase was observed in the field-cooled conditions. The transformation of T to MA phase was realized through an intermediate Mc phase. The results also represent conclusive and direct evidence of a Mc to MA phase transformation in field-cooled conditions. Beginning from the zero-field-cooled condition, a R→MA→Mc→T phase transformational sequence was found with an increasing electric field at a fixed temperature. Upon removal of the field, the MA phase was stable at room temperature. With increasing the field, the transformation temperature from T to Mc and from Mc to MA phase decreased, and the phase stability ranges of both T and Mc phases increased. Upon removal of the field, the phase transformation from R to MA phase was irreversible, but from MA to Mc was reversible, which means that MA 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.

• 이은구(조선대학교 신소재공학과) | Lee, Eun-Gu