Thermodynamic properties of the Sb6O13 and Ca6Sb2O11-σ
摘要
This investigation employed high-temperature drop calorimetry to determine the high-temperature heat capacities (Cp) of Sb6O13 and three polymorphs of perovskite-type Ca6Sb2O11-δ: cubic (Cub), tetragonal (Tet), and orthorhombic (Orth). The temperature-dependent Cp relationships for Sb6O13, Cub-Ca6Sb2O11, Tet-Ca6Sb2O11 and Orth-Ca6Sb2O11-δ were derived as: Cp (Sb6O13) = 493.05 + 6.61 × 10−11 T-9498750 T−2 (573–973 K); Cp (Cub-Ca6Sb2O11) = 550 + 2.00× 10−6 T −22848000 T−2 (573–1273 K); Cp (Tet-Ca6Sb2O11) = 481.03 + 1.92 × 10−9 T-7780332.5 T−2 (573–1273 K); Cp (Orth-Ca6Sb2O11-δ) = 492.474 + 3.63× 10−9 T−8940348.47 T−2 (573–1273 K), and then used for computing changes in entropy and Gibbs free energy.