Superconductivity in CoSr2(Y1−xCax)Cu2O7+δ

✍ Scribed by Y. Morita; H. Yamauchi; M. Karppinen

• Publisher: Elsevier Science
• Year: 2003
• Tongue: English
• Weight: 364 KB
• Volume: 127
• Category: Article
• ISSN: 0038-1098
• DOI: 10.1016/s0038-1098(03)00486-1

✦ Synopsis

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, CoSr 2 ðY 12x Ca x ÞCu 2 O 7þd (Co-1212), were investigated. The as-air-synthesized samples up to x ¼ 0:4 were found essentially oxygen stoichiometric ð20:03 # d # 0:00Þ: 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 8C for 30 min in the presence of Ag 2 O 2 as an excess oxygen source induced bulk superconductivity in these samples. The highest T c was obtained for the high-oxygenpressure treated x ¼ 0:3 sample at , 40 K.