Bulk superconductivity observed in (Co,Cu)(Sr,Ba)2(Y,Ca)Cu2Oy

Effects of cobalt substitution for copper in Cu(Ba,Sr)(2)(Y,Ca)Cu2Oy [Cu1212] on its superconducting properties were systematically studied. Bulk superconductivity was confirmed in wide compositional range of the (Cu,Co)(Ba,Sr)(2)-(Y,Ca)Cu2Oy system and their T-c's were enhanced by annealing under high oxygen pressure. In addition, it was indicated that partial strontium substitution for barium suppresses the incorporation of cobalt into the CuO2 planes. Hole doping with moderate concentration and suppression of cobalt incorporation in the CuO2 planes are believed to result in the new superconducting compositions showing high T-c's exceeding 70 K. (c) 2005 Elsevier B.V. All rights reserved.