Critical exponents for anisotropic thermal expansion at ferroelectric Curie temperatures: Evidence for defect mechanisms

Abstract

The defect dynamical model of Sigov and Levanyuk is used to analyze a heretofore unsolved problem in ferroelectricity: the temperature change of anisotropic thermal expansion along the polar axis. For brominated tris-sarcosine calcium chloride a new expansion exponent in reduced temperature is found, in agreement with the Sigov-Levanyuk theoretical value, under the assumption that the change in thermal diffusion is proportional to the change in thermal expansion near Tc.