Abstract
Phase relations in the systems SrO-Y2O3-CuO-O2 and CaO-Y2O3-CuO-O2 at 1173 K were estab-lished by equilibrating different compositions in flowing oxygen gas at a pressure of 1.01 × 105 Pa. The quenched samples were examined by optical microscopy, X-ray diffraction (XRD), energy dis-persive analysis of X-rays (EDAX), and electron spin resonance (ESR). In the system SrO-Y2O3-CuO-O2, except for the limited substitution of Y3+ for Sr2+ ions in the ternary oxide Sr14 Cu24O41, no new quaternary phase was found to be stable. The compositions corresponding to the solid solution Sr14-xYxCu24O41 and the compound SrCuO2+δ lie above the plane containing SrO, Y2O3, and CuO, displaced towards the oxygen apex. However, in the system CaO-Y2O3-CuO-O2 at 1173 K, all the condensed phases lie on the plane containing CaO, Y2O3, and CuO, and a new quaternary oxide YCa2Cu3O6.5 is present. The quaternary phase has a composition that lies at the center of the non-stoichiometric field of the analogous phase YBa2Cu3O7-δ in the BaO-Y2O3-CuO-O2 system. The com-pound YCa2Cu3O6.5 has the tetragonal structure and does not become superconducting at low temperature. Surprisingly, phase relations in the three systems CaO-Y2O3-CuO-O2, SrO-Y2O3-CuO-O2, and BaO-Y2O3-CuO-O2 are found to be quite different.
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Jacob, K.T., Waseda, Y. Phase Relations in the Systems SrO-Y2O3-CuO-O2 and CaO-Y2O3-CuO-O2 at 1173 K. JPE 15, 401–405 (1994). https://doi.org/10.1007/BF02647560
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DOI: https://doi.org/10.1007/BF02647560