Field induced O-MC phase transition and domain structure evolution in Pb(Mg1/3Nb2/3)O3-0.34PbTiO3 single crystals under radial poling

Radial electric (E)-field induced periodic polarization rotation from orthorhombic (O) to MC-type monoclinic (MC) phase in Pb(Mg1/3Nb2/3)O3-0.34PbTiO3 (PMN-0.34 PT) single crystals has been studied by in situ polarized light microscope. The piezoelectric coefficient (d33∗) and dielectric permittivity (ε33T/ε0) were 1800 pm/V and 5100, respectively, for [100]-oriented MC samples, almost three times of those in [011]-oriented O phase crystals. The domain structure evolution from 1O to 4MC was confirmed based on the optical extinction rules and permissible domain configurations. Moreover, the phase transition sequences of [100]- and [011]-poled PMN-0.34 PT crystals were MC-Tetragonal (T)-Cubic (C) and O-T-C upon heating, respectively. Our findings suggest that the phase stability of this crystals is associated with the orientation of applied field and radial E-field can serve as a general strategy to get fundamental insights into large piezoelectric activity and anisotropic phase stability in ferroelectric single crystals.