C. B. Cai

Single and binary rare earth REBa2Cu3O7-delta films prepared by chemical solution deposition

In the present work, a series of single and binary rare earth REBa2Cu3O7-delta(REBCO, RE=Y, Ho etc.) thin films, such as YBCO, HoBCO and Y0.7Ho0.3BCO, were prepared by TFA-MOD process. Screw-growth mode and island-like surface were clearly observed in the present samples. Good c-axis orientation and high in-plane texture were identified in the all studied samples by measuring four circle X-ray diffractions (XRD). Theta-2Theta patterns of XRD showed no extra phases other than REBCO. As for HoBCO and Y0.7Ho0.3BCO thin films, the temperature dependences of resistance were investigated in various applied magnetic fields (< 9T) Irreversibility fields (Hirr), characterised with a criteria of zero resistance in R-T curves, showed a similar superconducting behavior between single and binary REBCO, i.e. no obvious changes in performance due to Ho doping in YBCO.

Artificial Multilayers of REBaCuO/YBaCuO and YBCO/CuO(Y2O3) for High-Performance Long Tapes of Coated Conductors Derived by Metal Organic Solution Deposition

Thick superconducting multilayer architectures consisting of alternate superconducting and superconducting layers DyBCO/YBCO and alternate superconducting and insulating layers YBCO/CuO(Y₂O₃) are developed on buffered Hastelloy tapes using a metal organic deposition process. It is revealed that multilayer intermittent structures for superconducting layers are effective to avoid the presence of microcracks that occur with increasing thickness, which are frequently observed in monolayer films of REBa₂Cu₃O_7−δ (REBCO, RE = Y, Gd, or other rare earth elements). This paper shows that the thicknesses of DyBCO/YBCO multilayer films can reach 2.8 μm with a homogeneous, dense and crack-free surface morphology. The out-plane FWHM of the YBCO (005) peaks and the critical current value reach 1.1° and 365 A/cm (77 K, self-field) for such a thick film consisting of DyBCO/YBCO multilayers. It is also revealed that the introduction of a CuO layer is effective to avoid the presence of a-axis grains and voids of the YBCO films, which are frequently observed in multilayer films. Note that the introduction of CuO shows little negative influence on the texture of multilayer structure, especially for the bottom CuO. However, the in-plane texture deteriorates seriously for Y₂O₃/YBCO/YBCO multilayer film. The critical current density of YBCO films with middle CuO and bottom CuO are 2.0 MA/cm² and 2.5 MA/cm² (77 K, self-field), respectively. The microstructure optimization including the texture, uniformity, crack, defect, and porosity in the multilayered films is probably the reason for the enhancement of superconducting performance.

Epitaxial growth and thermal dynamics of CeO2 buffer layer on textured Ni-W substrates for YBCO coated conductors

In present study, the biaxially textured CeO2 buffer layers on Ni-W substrates have been prepared by chemical solution deposition (CSD) with cerium acetate as the starting precursor, mixed with solvents of Propionic acid, Isopropanol and Acetylacetone. Typical XRD θ-2θ scans and the pole figure display well out-of-plane and in-plane textures of CeO2 films. SEM and AFM results suggest that the buffer layer have uniform and smooth surface. Meanwhile, the effects of heating rate on CeO2 formation starting from the precursor solution have been studied using differential thermal analysis (DTA). And the further analysis is given by XRD results for precursor xrogel at the corresponding temperature. Detailed high temperature optical microscope (HTOM) photographs investigate the surface characteristics evolved with temperature.