Structural, vibrational and dielectric studies of 0.91PMN–0.09PT single crystals

Abstract

Ferroelectric relaxor 0.91PbMg1/3Nb2/3O3–0.09PbTiO3 single crystals in a wide temperature range were studied using dielectric, x-ray powder diffraction and Raman scattering techniques. Dielectric studies show that without applying an external electric field, 0.91PMN–0.09PT exhibits typical relaxor behaviour with at 310 K (1 kHz), while after cooling in an electric field the transition from the relaxor state to the long-range ferroelectric one is observed at 270 K. X-ray powder diffraction reveals that 0.91PMN–0.09PT undergoes structural phase transition from cubic to rhombohedral symmetry (R3m) at Tc = 283 K. However, based on the results of Raman scattering, the existence of clusters with 1 : 1 order in the B-sublattice, leading to the doubling of the unit cell parameters, and the appearance of (Z = 2) space group symmetry above Tc, and R3m (Z = 2) below Tc were stated. These results indicate the special role played by the Pb ion dynamics. Correlated Pb ion displacements creating the polar nanoregions, and the temperature evolution of these nanoregions directly determine all physical properties of 0.91PMN–0.09PT. An overall view of the behaviour of this solid solution within a wide temperature range is presented.