On the existence of a homologous series of BamCum+nOy oxides with the cubic structure of the BaCuO2 oxide

Phase relations have been studied in the BaO-CuOx system in the range of 42.0-83.0 mol.% CuO at P(O2) = 21 kPa (air) by visual polythermal analysis (VPA), powder X-ray diffraction (XRD), differential thermal analysis (DTA), thermogravimetric analysis (TGA), chemical analysis (CA), and electron diffraction (ED) with simultaneous elemental analysis (EA) in a transmission electron microscope (TEM). The existence of discrete crystallization fields of barium-copper oxides of cation compositions Ba4Cu5Oy, Ba5Cu6Oy, Ba7Cu8Oy, Ba12Cu13Oy, and Ba24Cu25Oy, which have the cubic structure of the BaCuO2 oxide, is revealed in the studied region of the system. The oxides may be represented as members of a BamCum+nOy homologous series. The BaCuO2 oxide does not exist in the subsolidus region and does not have its own crystallization field. The oxygen-deficient oxide BaCuO1.78 of the cation composition (Ba:Cu) 1:1 with the BaCuO2 cubic structure is found in melted samples of the 50.0 mol.% CuO composition quenched at 1020-1060 °С.