THERMODYNAMICS AND PHASE-DIAGRAM OF THE BINARY-SYSTEM BI2O3-B2O3

We analyzed the thermodynamic data of the binary system Bi2O3-B2O3. Th e phase diagram contains five compounds, of which four melt congruentl y, and a miscibility gap, close to pure B2O3. The three sets of transf ormation data of Bi2O3, the enthalpy of mixing data in the liquid, and the critical point of the miscibility gap gave five equations for the excess Gibbs energy of mixing and five sets of values for the enthalp ies of formation of the binary compounds. The critical point data yiel ded another set of transformation data for Bi2O3. Using the monotectic composition and the enthalpy of mixing data also yielded a set of tra nsformation data for Bi2O3. The values obtained using the enthalpy of mixing data are the most reliable values.