THERMOANALYTICAL STUDY OF COMPOUND FORMATION IN THE BI2O3-PBO-CAO SYSTEM

Previous studies concerning the formation of compounds in binary syste ms of the type Bi2O3-MO and PbO-MO (M-Ca, Sr and Ca + Sr) have shown t hat the reactions which occur with the highest rate are those between Bi2O3 and CaO and between PbO and CaO. This work deals with the compet ition betweeen PbO and Bi2O3 in reaction with CaO, when the three abov e mentioned oxides coexist. DTA-TG analysis performed under non-isothe rmal conditions and X-ray diffraction determinations have shown that t he first reaction which occurs is that between Bi2O3 and PbO. On incre asing the temperature, the compound between Bi2O3 and PbO melts, leadi ng in the presence of CaO, to the preferential formation of 2CaO . PbO 2. Under non-isothermal conditions, up to 1173 K, in the ternary compo sitions investigated, the compound 3Bi(2)O(3) . 4CaO is also formed.