Phase equilibrium in the SeO2-Bi2O3 system

The subject of the present study is the system SeO2-Bi2O3 that comprises tw o oxides with low melting points. All batches are thermal treatment in quar tz ampoules, which are evacuated and sealed at a pressure P=0.1 Pa. On the basis of DTA (differential thermal analysis) and X-ray data, the most proba ble liquidus line of the system has been plotted. The eutectic composition lies about 90 mol% SeO2, with on eutectic temperature at 230 degreesC. Abov e 20 mol% Bi2O3 the liquidus temperature extremely increases. The formation of three compounds is proved: Bi2Se3O9 and Bi2Se4O11 are melting incongrue ntly at 540 and 350 degreesC respectively and Bi2SeO5 congruently at 915 de greesC.