Landau theory-based analysis of grain-size dependence of ferroelectric-to-paraelectric phase transition and its thermal hysteresis in barium titanateceramics

Ferroelectric barium titanate ceramics with grain sizes in the range (0.5, 20) mu m were used for a comparative study of grain-size influence on the f erro-para phase transition and its thermal hysteresis. The investigations w ere performed by recording the temperature dependence of the dielectric con stant, heat capacity and pyrocharge. The experimental results have been ana lysed in the framework of Landau-Devonshire theory. The grain-size dependen t Landau coefficients of the free energy have been derived from our experim ental data and used to compute the grain-size dependence of the theoretical transition interval related to the thermal hysteresis. The good qualitativ e agreement between theory and experiment recommends the size dependent Lan dau coefficients as a way to improve the modelling of the size dependent fe rro-para phase transition in ceramics.