Studies in the BaO2–BaO–CuO system

Abstract

The complex ternary system Ba-Cu- O has been re-visited in 0.1 MPa oxygen pressure. It is established that for such pressure, the $\text{BaO}{}_{\mathrm{<mtext>2</mtext>}}\text{=}\text{BaO+}\text{1}\text{2}\text{O}{}_2$ reaction has an important role for reaching the equilibrium state. The pathway for the phase formation is then described in ternary sections BaO₂-BaO-CuO. We have specified the temperatures and the forming reactions of the 3 compounds in the system: Ba₂CuO_3.04 decomposes by peritectic-like reaction at 1033°C and shows a structural transition from orthorhombic to tetragonal for at 825°C, BaCuO₂ is a congruent melting compound at 1035°C and Ba₂Cu₃O_5.5 undergoes a peritectoïdic decomposition into BaCuO₂ and CuO at 893°C.