Some details of the ternary system Bi₂O₃-CaO-CuO

Abstract

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 β and α′'₁ and the stoichiometric compounds Bi₂CaO₄, Bi₆Ca₄O₁₃, and Bi₂Ca₂O₅ were found to exist for 675 °C≦T≦780 °C. Above 780 °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 °C all the Bi-Ca oxides mentioned above are in equilibrium with CuO. At 820 °C, a wide liquidus field is dominating so that these quasibinary equilibria disappear. For 780 °C<T<820°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.