Study on Annealing Treatment and Sr/Ca Ratio for Pb-Sr-Y-Ca-Cu-O Ceramics with “1212” Structure

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Abstract
The annealing effects of “1212” lead cuprate in a Pb-Sr-Y-Ca-Cu-O system were investigated. Samples with a nominal composition of (Pb0.7Cu0.3)Sr2(Y1-x Ca x )Cu2O y (x=0.4-0.7) were annealed at various temperatures in oxygen. The x=0.5 sample, which was annealed at 800°C and then quenched, exhibited the highest T c(zero resistivity) of 48 K. It was found that there were three different types, two tetragonal phases and one orthorhombic phase, in the “1212” of x=0.5. It was considered that the phase transformation was caused by different oxygen contents. Samples with a nominal composition of (Pb0.7Cu0.3)Sr2+z (Y0.5Ca0.5-z )Cu2O y (z=±0.3) were also prepared. Deviation from z=0.0 in the composition induced degradation of the superconductivity.