Thermodynamic Properties of Lutetium Stannate Lu<sub>2</sub>Sn<sub>2</sub>O<sub>7</sub> in the Temperature Range 0–1871 K

Lutetium stannate with a pyrochlore structure was synthesized using solid state reaction route. The heat capacity of the polycrystalline Lu2Sn2O7 in the temperature range 7.99–1871 K was measured by adiabatic and differential scanning calorimetry methods. Entropy, enthalpy change, and derived Gibbs energy were calculated from the smoothed heat capacity data. The Gibbs free energy of Lutetium stannate from simple substances was estimated, using the ΔfS°(Т) values obtained in this work and the ΔfH°(Т) values from the literature. The temperature dependence of the cubic crystal lattice parameter and the value of the coefficient of thermal expansion in the temperature range 300–1273 K were determined by high-temperature X-ray diffraction.