Thermochemische Untersuchungen am System Bi/Se/O III. Zum quasibinären System Bi2O3 –Bi2Se3 und zum ternären Bereich Bi2O3– Bi2O2Se – Se – SeO2/Thermochemical Investigations on the System Bi/Se/O III.The Quasy Binary System Bi2O3-Bi2Se3and the Ternary Ran

Only the ternary phase Bi2O2Se is shown to exists in the thermodynamical equilibrium in the investigated ternary system on the binary line Bi2O3-Bi2Se3. Its thermal decomposition was measured in a quartz membrane zero manometer. The enthalpy of formation and the standard entropy were derived from the temperature function of the decomposition equilibrium: ⊿H°f(Bi2O2Ses,298) = -104,6 ±4,0 kcal/mol S°(Bi2O2Ses,298) = 43 ± 3 cal/K·mol. The coexistence ranges in the ternary region Bi2O3- SeO2- Bi2O2Se-Se were followed by X-ray diffraction, IR spectroscopy and total pressure measurements of binary and ternary compositions.