Binary and ternary compounds, phase diagrams and contaminations in the YO 1.5 -BaO-CuO system auxiliary to superconducting ceramics

Abstract

The binary phases and compatibilities of the BaO-CuO, YO 1.5-BaO and YO 1.5-CuO systems are discussed. The different variants of YBa 2Cu 3O 7-y, are shown in dependence on y. So far reported existence of the ternary compounds (in the ratio Y:Ba:Cu) 1:3:2,1:4:3,1: :2:4,1:5:3,3:8:5,2:3:5 and 1:4:2 are questioned.The ternary phase diagram and pseudobinary cuts of the YCuO 2.5-(1:2:3)-BaCuO 2 and Y 5BaO 8.5-(1:2:3-2:1:1)-Ba- 3Cu 5O 8 are reviewed. The distorting effect of impurities from air (e.g. oxycarbonates formation) and/or from the sample holder (e.g. Pt-substituted compounds) is analysed. On basis of the 1:2:3 structural model hypothetical superconducting compounds 1:1:2, 1:3:4 and 1:2:4 are predicted assuming double layers of. corner-sharing square-planar CuO 4 units.