Electrostrictive Coefficient of a Rocksalt-Type Oxide MgO

Abstract

The electric-displacement-related electrostrictive coefficient Q_h of a rocksalt-type oxide, MgO, has been determined as 0.16 m⁴C⁻² by measuring the hydrostatic pressure dependence of the reciprocal permittivity (Q_h=(1⁄2)[∂(1⁄ε₀ε)⁄∂p]). Comparing the Q_h values of several rocksalt- and perovskite-type fluorides and oxides, a general empirical rule is proposed that the electrostrictive coefficient of fluorides is larger than that of oxides with the same crystal structure and the Q_h of the rocksalt is larger than that of the perovskite. A simple shell model can describe this general tendency in conjunction with the Born-Mayer potential, where the electrostrictive coefficient is represented in proportion to a⁵⁄Z² (a: cation-anion distance; Z: ionic valence).