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

Ferroelectric barium titanate ceramics with grain sizes in the range (0.5, 20) µm were used for a comparative study of grain-size influence on the ferro-para phase transition and its thermal hysteresis. The investigations were performed by recording the temperature dependence of the dielectric constant, heat capacity and pyrocharge. The experimental results have been analysed in the framework of Landau-Devonshire theory. The grain-size dependent Landau coefficients of the free energy have been derived from our experimental data and used to compute the grain-size dependence of the theoretical transition interval related to the thermal hysteresis. The good qualitative agreement between theory and experiment recommends the size dependent Landau coefficients as a way to improve the modelling of the size dependent ferro-para phase transition in ceramics.