Microstructure and properties of MOCVD-derived Gd x Y1−x Ba2Cu3O7−δ films with composition fluctuations
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The effects of Gd content on crystalline orientation, microstructure and superconductivity of Gd x Y1−x Ba2Cu3O7−δ (GdYBCO) films were systematically investigated. By varying the Gd content in the liquid precursor without changing the total amount of rare earth elements, series of GdYBCO films with x values of 0, 0.1, 0.3, 0.5, 0.7, 0.9 and 1.0 were fabricated by metal organic chemical vapor deposition (MOCVD). X-ray diffraction (XRD) and scanning electron microscope (SEM) analysis revealed that Gd introducing could restrain the formation of CuYO2 phase, but induce a-axis growth of GdYBCO film. The increase of x from 0 to 0.5 leads to enhancing critical current density at self-field and 77 K (J csf) from 1.8 to 2.8 MA·cm−2, which benefits from the decrease in CuYO2 impurities and improvement of in-plane texture from 5.0° to 4.3°. However, raising x from 0.5 to 1.0 gives rise to abundant a-axis growth of film and degradation of in-plane texture from 4.3° to 5.4°, consequently resulting in the decrease of J csf from 2.8 to 0.8 MA·cm−2. Even though J csf has not varied monotonically, the critical transition temperature of GdYBCO films linearly increases from 90.75 to 92.25 K and the in-field performance at magnetic field (B) of 0–1.1 T and 77 K as well as B parallel to film normal is also superior with Gd content increasing.
KeywordsGd content GdYBCO MOCVD Microstructure Flux pinning
This study was financially supported by the National Science Foundation of China (No. 91421110), the National High Technology Research and Development Program of China (No. 2014AA032702), the National Basic Research Program of China (No. 2015CB358600), the Sichuan Youth Science and Technology Innovation Research Team Funding (No. 2011JTD0006) and the Sichuan Provincial Fund for Distinguished Young Academic and Technology Leaders (No. 2014JQ0011).
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