CeO2 compatibility with YBa2Cu3O7-delta in superconducting-film multilayers

High-quality superconducting (T-c approximate to 90 K, j(c)> 10(6) A/cm(2) at 77 K) epitaxial (001) YBa2Cu3O7-delta films were grown by laser ablation on (001) CeO2/(1 (1) under bar 02) Al2O3. An interaction between YBa2Cu3O7-delta and CeO2 would influence the structure and the superconducting parameters. A marked degradation of the superconducting transition temperature (T-c=74 K) was observed when twenty 2-nm-rhick CeO2 layers were inserted equidistantly into a (001) YBa2Cu3O7-delta film (200 nm). BaCeO3 crystalline inclusions were detected by xray diffraction. X-ray-absorption fine-structure investigations at the Cu-K edge indicate that Ce substitutes for Y in YBa2Cu3O7-delta. Near-edge x-ray-absorption studies indicate that the valence of Ce incorporated into the YBa2Cu3O7-delta regions of the multilayer structure is also +4.