Structural Transformation of Relaxor PbMg1/3Nb2/3O3 under Electric Field Switching

One from the most important features of relaxors is the possibility of inducing a stable ferroelectric phase in them by applying an electric field. This induced phase transition has been multiply investigated; in particular, the structural changes during the transition and its kinetics were traced. However, the processes occurring under electric field switching remain little-studied, and the structural transformation during switching generally has not been investigated at all. To fill in this gap, the temporal evolution of the pattern of Bragg and diffuse X-ray scattering in classical relaxor PbMg1/3Nb2/3O3 at T = 175 K during multiple switching of the direction of a dc external field E = ± 6.25 kV/cm has been traced. It is shown that the glasslike state decays and a mixed ferro-glass phase is formed after switched on a field. Switching the field sign leads to a rise of dipole-glass correlations; however, no signs of occurrence of an inhomogeneous state with limited regions of dipole-glass and ferroelectric phases were found. Switching the field to the initial direction causes rapid formation of the ferroelectric phase, without any rise in the dipole-glass correlations. A repeated switching leads to a decrease in the Bragg scattering intensity, related to the long-range order. This effect is presumably due to the occurrence of random weakly correlated ionic displacements, violating the long-range order.