Orientation dependence and electric-field effect in the relaxor-based ferroelectric crystal (PbMg1/3Nb2/3O3)0.68(PbTiO3)0.32 -: art. no. 104113

Dielectric permittivities, polarization-electric-field hysteresis loops, and domain structures have been measured as a function of temperature in relaxor-based ferroelectric single crystals (PbMg1/3Nb2/3O3)(0.68) (PbTiO3)(0.32) (PMN-32% PT) for [110](cub) and [211](cub) orientations. Contrary to the pure PbMg1/3Nb2/3O3 (PMN), PMN-32% PT exhibits apparent crystallographic orientation dependences of dielectric permittivities, polarizations, domain structures and phase transitions. With a prior field-cooled treatment, a field-induced state, perhaps of orthorhombic symmetry, is evidenced and coexists with the rhombohedral symmetry in the low-temperature region. This field-induced phase is manifested by an extra dielectric peak observed near 373 K for the [211](cub) orientation. A relaxation mechanism which is responsible for the so-called diffuse phase transition crosses a wide temperature region of similar to340-400 K and results from fluctuations between rhombohedral and tetragonal states. In order of increasing temperature (without a prior field-cooled treatment), PMN-32% PT undergoes successive phase transformations: rhombohedral phase --> coexistence of rhombohedral and tetragonal phases tetragonal phase coexistence of tetragonal and cubic phases --> cubic phase.