Neutron diffraction study of electrostrictive coefficients of prototype cubic phase of relaxor ferroelectric PbMg_1/3Nb_2/3O₃

The electrostrictive coefficients of prototype cubic phase of PbMg_1/3Nb_2/3O₃ are studied using a high-resolution neutron powder diffraction experiment. The key idea of the approach is to "eliminate" from the material the inhomogeneity related to the presence of the double-phase mixture "polar regions/nonpolar matrix," and to study two structurally homogeneous states: prototype cubic at temperatures above 600 K and rhombohedral ferroelectric at temperatures below 220 K. The obtained value of volumetric electrostrictive coefficient, Q_h=(8.3±1.0)×10^-2 ×(m⁴/C²), is consistent with those of other perovskite ferroelectrics with a prototype cubic phase.