Primary crystallization field of YnBamCum + nOy oxides with YBa2Cu3O6 tetragonal structure

The phase composition of specimens in the primary crystallization field of the Y n Ba m Cu m + n O y oxide series with compositions of (Y:Ba:Cu) 235, 123, and 257 was investigated by means of X-ray powder diffraction, X-ray microprobe analysis, electron diffraction, and high resolution imaging in a transmission electron microscope. Y n Ba m Cu m + n O y oxides have the YaBa2Cu3O6 tetragonal structure and can be represented in the general form as 123 oxides. It was found that the crystallization field of 123 oxides corresponds to the crystallization fields of the Ba m Cu m + n O y oxide series with the BaCuO2 cubic structure. These crystallization fields are located in the matrix phase diagram of the BaO-CuO x system at P(O2) = 21 kPa in the range of 50–90 mol % CuO and 910–1000°C. The 123 oxides are formed according to an intercalation mechanism with the participation of barium-copper oxide matrices with the composition (Ba: Cu) 3: 5, 2: 3, and 5: 7