Superconductivity in CoSr2(Y1−xCax)Cu2O7+δ |
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Authors: | Y MoritaH Yamauchi M Karppinen |
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Institution: | Materials and Structures Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503, Japan |
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Abstract: | The roles of aliovalent CaII-for-YIII substitution and high-pressure-oxygen annealing in the process of ‘superconducterizing’ the Co-based layered copper oxide, CoSr2(Y1−xCax)Cu2O7+δ (Co-1212), were investigated. The as-air-synthesized samples up to x=0.4 were found essentially oxygen stoichiometric (−0.03≤δ≤0.00). These samples, however, were not superconducting, 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 500 °C 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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Keywords: | 74 10 +v 74 25 Dw 74 62 Bf 74 72 Jt |
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