High-Temperature Heat Capacity of Bismuth Oxide and Bismuth-Zinc Double Oxide with the Sillenite Structure

Bismuth oxide and Bi2O3-based compounds are of practical importance in view of their valuable properties and for a long time attract considerable attention of scientists [1 – 4]. At the same time, there are certain problems relating to the obtaining materials. It is attributed to the fact that many Bi2O3-based oxide compounds can be in metastable state [4 – 6]. Phase equilibria in such systems can be improved with the use of thermodynamic modeling. To do this would require data on the thermodynamic properties of original oxides as well as complex oxide compounds over a wide temperature interval. Although Bi2O3-based compounds are used extensively, their properties call for additional investigations. In the first place, this is true for pure Bi2O3. It forms α, β, γ and δ polymorphous modifications in different temperature ranges [7]. By now there are data on the heat capacity of Bi2O3. The values of Cp for this oxide at 298-800 K are given in [8] by Eq. (1), J/(mole·К):