The fact that the polarization-related electrostrictive coefficients Q in the relaxor type ferroelectrics are almost an order of magnitude smaller than in most normal ferroelectric perovskites can be explained under the assumption that the temperature dependence of the soft-mode TO phonon frequency is given as omega **2//T//O equals A(T minus T//c), where the coefficient A in relaxor ferroelectrics is an order of magnitude smaller than the value in normal ferroelectric perovskites. The assumption also explains why the Curie-Weiss constants, C, in the relaxor crystals are several times larger than in the normal ferroelectrics. The soft-mode frequency in Pb(Mg//1/////3Nb//2/////3)O//3 crystals is predicted to be below 10 cm** minus **1 near the mean Curie temperature.
All Science Journal Classification (ASJC) codes
- Materials Science(all)