Electrostrictive terms have been introduced into the simple Kittel free-energy function for antiferroelectrics. An additional coefficient W is found to be required to take account of the interaction with the sublattice polarizations, and Q and W values have been calculated from experimental data for typical antiferroelectric perovskites PbZrO3 and Pb(Mg 1/2W1/2)O3. Consideration of several ferro- and antiferroelectric perovskites suggests that the magnitude of Q is not affected strongly by ferro- or antiferroelectricity, but that it does depend quite strongly upon any disorder in the cation arrangement. An empirical rule that the product of the electrostrictive Q coefficient and the Curie Weiss constant C is almost the same for all ferro- and antiferroelectric perovskites is proposed (QhC = 3.1±0.4×103 m4 C -2 K). A very simple "rattling ion" model is shown to give a simple intuitive explanation of the observed results.
All Science Journal Classification (ASJC) codes
- Physics and Astronomy(all)