Equilibrium phase diagram for the system PbO-CaO-CuO

In order to obtain essential information on the formation process of the high-T_c phase in the Bi, Pb-Sr-Ca-Cu-O system, phase equilibria in the system PbO-CaO-CuO have been studied, mainly by x-ray diffraction analysis and thermal analysis. Temperature versus composition diagrams were established for the systems PbO-CuO(Cu₂O) and PbO(PbO₂)–CaO in air. Three invariant points were detected in these systems: a eutectic reaction (PbO + Ca₂PbO₄ = L) at 847 ± 6°C, a peritectic reaction (Ca₂PbO₄ = L + CaO) at 980 ± 2°C, and a eutectic reaction (PbO + CuO = L) at 789 ± 3°C. For the system PbO(PbO₂)-CaO-CuO, subsolidus phase equilibrium in air was established. The liquidus was also examined at 780, 800, and 820°C, and a ternary (PbO-Ca₂PbO₄-CuO) eutectic point was detected at 772 ± 6°C.