New Phases in the CaO-M2O3-CuO (M = Nd,Gd,Y) systems at 1000 degrees C

New layered cuprates with the general stoichiometry Ca2+xM2-xCu5O10 have been characterized for M = Nd, Gd, and Y. This paper reports these insulating phases having structures closely related to that of NaCuO2 and contain one-dimensional chains constructed from edge-sharing [CuO4] square planes. The x-ray patterns of these ternary cuprate phases are complicated by strong reflections from both incommensurate and commensurate supercells which result from the ordering of the Ca2+ and M3+ ions in the structure. The stoichiometry range, and resultant Cu valences in these cuprates depend upon the nature of the trivalent ion. Ca-rich and trivalent-rich compositions can be prepared for M = Nd and Gd, but only Ca-rich compositions were formed in the Y system. No other ternary phases are observed under the conditions of this study, 1000 degrees C in air, and the solid-state equilibria are dominated by the single ternary phase identified above