Thermochemical investigation of δ-Bi2O3 doped by Re2O7 and Sm2O3

• We synthesized new phase Bi12.5Sm1.5ReO24.5.
• We measured formation enthalpy of Bi12.5Sm1.5ReO24.5.
• The phase is thermodynamically stable with respect to decomposition into binary oxides at room temperature.

The Bi12.5Sm1.5ReO24.5 phase has been synthesized for the first time. The preparation of Bi12.5Sm1.5ReO24.5 has been carried out by solid-state reaction from Bi2O3, Sm2O3, and Re2O7. The X-ray measurements have showed that Bi12.5Sm1.5ReO24.5 was cubic structure (space group Fm3m). The standard molar enthalpy of formation of Bi12.5Sm1.5ReO24.5 has been determined by solution calorimetry combining the enthalpies of dissolution of Bi12.5Sm1.5ReO24.5 and 6.25Bi2O3 + 0.75Sm2O3 + 0.5Re2O7 mixture in 2 M HCl and literature data. It has been obtained that above-mentioned phase is thermodynamically stable with respect to their decomposition into binary oxides at room temperatures.