SOME DETAILS OF THE TERNARY-SYSTEM BI2O3-CAO-CUO

Before investigating the ternary system Bi2O3-CaO-CuO, a revision of the binary bounding system Bi2O3-CaO was first necessary. In the range between 20 and 70 mol % CaO the solid solutions beta and alpha1'' and the stoichiometric compounds Bi2CaO4, Bi6Ca4O13, and Bi2Ca2O5 were found to exist for 675-degrees-C less-than-or-equal-to T less-than-or-equal-to 780-degrees-C. Above 780-degrees-C a new high temperature compound with the formula Bi6Ca5O14 has been identified. The X-ray powder diffraction data, unit cell dimensions, as well as the space group, have been reported. The ternary system contains no intermediate compounds and also no solubility was found for the binary bounding phases. Below 780-degrees-C all the Bi-Ca oxides mentioned above are in equilibrium with CuO. At 820-degrees-C, a wide liquidus field is dominating so that these quasibinary equilibria disappear. For 780-degrees-C < T < 820-degrees-C the new compound Bi6Ca5O14 forms an equilibrium with Ca2CuO3 and CuO. Other equilibria are deduced. For a fixed ternary composition the reaction path of the sintering process was investigated as a function of time and temperature.