Standard Enthalpies of Formation of the Bi2Mo3O12, Bi6Mo2Te2O21, and Bi2Te2O8 Complex Oxides

The tellurium molybdenum bismuth complex oxides Bi2Mo3O12, Bi6Mo2Te2O21, and Bi2Te2O8, promising starting materials for the preparation of bismuth-containing tellurite–molybdate glasses, have been synthesized by heating accurately weighed amounts of orthotelluric acid and ammonium heptamolybdate and bismuth nitrate crystal hydrates and identified by X-ray diffraction. Using reaction calorimetry, the standard enthalpies of formation of the complex oxide have been determined to be −2940.3 ± 39.8 kJ/mol for Bi2Mo3O12, −4128.6 ± 66.2 kJ/mol for Bi6Mo2Te2O21, and −1383.3 ± 11.5 kJ/mol for Bi2Te2O8. These values have been calculated as the difference between the standard enthalpies of solution of the complex oxide and mixtures of constituent binary oxides of corresponding content in concentrated hydrochloric acid.