Phase transformation via a monoclinic phase in relaxor-based ferroelectric crystal (PbMg1/3Nb2/3O3)1-x(PbTiO3)x -: art. no. 020102

A monoclinic phase is evidenced between rhombohedral and cubic phases in a <111>-cut single crystal (PbMg1/3Nb2/3O3)(0.67)(PbTiO3)(0.33) (PMN-33% PT) from observation of domain structures. Near 360 K the structure begins to distort from the rhombohedral toward the tetragonal phase through monoclinic domains (probably M-A type but perhaps M-B type). However, the present <111>-cut crystal seems to disfavor the tetragonal phase and persists in the monoclinic phase up to Tsimilar to420 K, where the cubic phase begins to develop. Temperature-dependent orientations of optical indicatrices of domains indicate polarization rotations within the monoclinic planes. In addition, a previously electric-field-cooled process enhances a long-range transformation.