Preparation of Ca-Substituted Y-Ba-Cu-O “124” Phase Thin Films by Magnetron Sputtering and Their Thermal Stability

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Abstract
Calcium-substituted Y-Ba-Cu-O “124” nearly single-phase thin films were prepared by sputtering at 550°C and annealing in oxygen at 750°C for 50 hours. T c(on) and T c(zero) values were 87 K and 65 K, respectively. At higher deposition temperatures, the as-grown “123” phase was not completely transformed into the “124” phase. The Ca-substituted “124” phase thin films were stable, and T c(on) did not change below 600°C, even in pure nitrogen. However, at over 600°C, in nitrogen the films changed to the “123” phase and oxygen defects in the resultant “123” phase increased, and the T c value dropped.