Phase Equilibrium in the SeO2–Bi2O3 System

The subject of the present study is the system SeO2-Bi2O3 that comprises two oxides with low melting points. All batches are thermal treatment in quartz 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 probable liquidus line of the system has been plotted. The eutectic composition lies about 90 mol% SeO2,with on eutectic temperature at 230°C. Above 20 mol% Bi2O3 the liquidus temperature extremely increases. The formation of three compounds is proved:Bi2Se3O9 and Bi2Se4O11 are melting incongruently at 540 and 350°C respectively and Bi2SeO5 congruently at 915°C.