Enthalpy increments and thermodynamic functions of rare earth samarium titanates RESmTi₂O₇(s) (RE = Gd,Dy)

Abstract

Enthalpy measurements have been taken on GdSmTi₂O₇ and DySmTi₂O₇ by using a high-temperature differential calorimeter at temperature between 800 and 1655 K. Thermodynamic function, such as heat capacity, entropy and Gibbs energy functions of GdSmTi₂O₇ and DySmTi₂O₇, was derived using the data obtained in this study. The results are presented and compared with the data available in the literature. The polynomial expression of enthalpy increments obtained for GdSmTi₂O₇(s) and DySmTi₂O₇(s) in the temperature range 298–1700 K is given as: $\begin{aligned} H_{\text{T}}^{0} - H_{298}^{0} / {\text{J}}\,{\text{mol}}^{ - 1} & = 252.961\,T \, + 1.596 \times 10^{ - 2} \,T^{2} + 3.705 \times 10^{6} \,T^{ - 1} - 89{,}265\quad ({\text{GdSmTi}}_{2} {\text{O}}_{7} ) \\ H_{\text{T}}^{0} - H_{298}^{0} / {\text{J}}\,{\text{mol}}^{ - 1} & = 256.504\,T \, + 1.576 \times 10^{ - 2} \,T^{2} + 3.531 \times 10^{6} \,T^{ - 1} - 89{,}721\quad \left( {{\text{DySmTi}}_{2} {\text{O}}_{7} } \right). \\ \end{aligned}$