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Superconductivity in CoSr2(Y1-xCax)Cu2O7+d

Y. Morita·H. Yamauchi·M. Karppinen
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Abstract

The roles of aliovalent Ca(II)-for-Y(III) substitution and high-pressure-oxygen annealing in the process of "superconducterizing" the Co-based layered copper oxide, CoSr2(Y1-xCax)Cu2O7+d (Co-1212), were investigated. The as-air-synthesized samples up to x = 0.4 were found essentially oxygen stoichiometric (-0.03 <= d <= 0.00). These samples, however, were not superconductive, suggesting that the holes created by the divalent-for-trivalent cation substitution are trapped on Co in the charge reservoir. Ultra-high-pressure heat treatment carried out at 5 GPa and 500C for 30 min in the presence of Ag2O2 as an excess oxygen source induced bulk superconductivity in these samples. The highest Tc was obtained for the high-oxygen-pressure treated x = 0.3 sample at ~40 K.

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Y. Morita, H. Yamauchi, M. Karppinen. 2003-05-09. Superconductivity in CoSr2(Y1-xCax)Cu2O7+d. https://doi.org/10.1016/s0038-1098(03)00486-1

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