Highly epitaxial YBa2Cu3O7−δ films grown on gradient La2−x Gd x Zr2O7-buffered NiW-RABiTS using all sol–gel process
The overall purpose of this work is to develop a reliable and low-cost technique for fabrication of coated conductors (CCs) on the flexible substrates, and to understand the effects of oriented growth and microstructure on the superconducting performance of CCs in-depth. The investigations of gradient La2−xGdxZr2O7 buffer architecture and YBa2Cu3O7−δ (YBCO) film on Ni-5at%W rolling-assisted biaxially textured substrate using all sol–gel process are reported. Combining x-ray diffraction and transmission electron microscopy (TEM) analysis, it is revealed that the gradient buffer architecture with increased lattice constant along the direction of film growth has an excellent c-axis orientation, while the inversed gradient architecture with decreased lattice constant shows the deteriorated orientation, indicating that the highly epitaxial growth mechanism most likely related to the interfacial lattice matching degree. The detailed analysis of YBCO films grown on gradient La2−xGdxZr2O7 under different deposition parameters, and the influence of microstructure on electrical properties are systematically discussed using x-ray diffraction, rocking curve test, scanning electron microscopy and TEM observations. Finally, the excellent biaxial texture YBCO film on gradient La2−xGdxZr2O7 buffer architecture is prepared at a proper heat-treatment temperature of 780 °C, and the full width at half maximum of ϕ-scan and ω-scan are 5.9° and 6.4°, respectively. The critical transition temperature Tc,onset of the as-prepared YBCO film is 90 K. With elevating the temperatures, the appearance of a large number of weak-link and amorphous regions, being indicative of the microstructural collapse, is mainly responsible for the reduced superconductivity.
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