The effects of Ca2+substitution for Y3+and La3+substitution for Ba2+in YBa2Cu3O7on the structural and superconducting properties were studied to control the average copper charge. Single-phase tripled perovskites were obtained for 0≦x≦0.2 and 0≦x≦1.0 for Ca and La doped series, respectively. A slight decrease of Tcwith increasing x was found for small x values for both kinds of substituted specimens prepared by furnace cooling in air. Oxygen annealing experiments were also carried out. These suggested that the superconduction in the Y-Ba-Cu-O system cannot be interpreted only by oxygen content or average copper charge.
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