Intermediate ferroelectric orthorhombic and monoclinic M_B phases in [110] electric-field-cooled Pb(Mg_1∕3Nb_2∕3)O₃–30%PbTiO₃ crystals

Structural phase transformations of [110] electric-field-cooled Pb(Mg_1∕3Nb_2∕3)O₃-30%PbTiO₃ (PMN-30%PT) crystals have been performed by x-ray diffraction. A phase sequence of cubic (C)→ tetragonal (T)→ orthorhombic (O)→ monoclinic (M_B) was found on field cooling (FC); and a rhombohedral (R)→M_B→O sequence was observed with increasing field, beginning from the zero-field-cooled condition at room temperature. The application of the [110] electric field induced a dramatic change in the phase sequence in the FC condition, compared to the corresponding data for PMN-30%PT crystals in a [001] field, which shows that the phase sequence in the FC condition is altered by the crystallographic direction along which a modest electric field (E) is applied. Only when E is applied along [110] are intermediate O and M_B phases observed.