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YBa 2 Cu 3 O 7 − x (YBCO) films of 110 nm thickness were prepared on LaAlO 3 (LAO) substrates via the sol–gel method. Subsequently, about 400 nm thick Ba 0.09 Sr 0.91 TiO 3 (BST) films were epitaxially grown on the YBCO and LNO films surface; the BST films exhibited a strong c -axis orientation. The dielectric adjustability and relative dielectric constant was investigated in the range of 300-83 K. Results indicate that the tunability of the Ba 0.09 Sr 0.91 TiO 3 /YBa 2 Cu 3 O 7 − x (BST/YBCO) displayed an increase relative to c -axis-oriented BST on LaNiO 3 (LNO). The tunability was further enhanced as the operating temperature decreased, yet the loss tangent (tan δ ) decreased. The tunability and the tan δ at 100 kHz and 83 K were 58% and 0.029, respectively. [ABSTRACT FROM AUTHOR]

YBa 2 Cu 3 O 7-δ /BaZrO 3 (YBCO/BZO) composite film with enhanced flux-pinning performance was prepared on LaAlO 3 (LAO) substrate via a fluorine-free sol-gel method in combination with a novel photosensitive sol-gel lithography technique. Owing to the difference of lattice mismatch between the interfaces of YBCO/LAO and YBCO/BZO, high-density stacking faults were successfully introduced into YBCO matrix, which has been confirmed by XRD and HRTEM analysis. Magnetization measurement results indicate that YBCO/BZO composite film has a stronger current-carrying capacity than the pure YBCO film especially under applied magnetic fields. However, the critical current density of YBCO/CeO 2 composite film is much lower than that of the pure YBCO film at all the applied magnetic fields due to the chemical reaction between YBCO and CeO 2. Therefore, it can be concluded that the flux-pinning performance of YBCO film can be improved by the lattice distortions within YBCO matrix as long as the metal oxide microarrays cannot react with YBCO films. • YBa 2 Cu 3 O 7-δ /BaZrO 3 composite film was fabricated by a novel photosensitive fluorine-free sol-gel lithography technique. • High-density stacking faults were introduced into YBCO film, resulting in the lattice distortions. • The enhanced flux pinning force and current-carrying capacity of YBCO films were achieved. [ABSTRACT FROM AUTHOR]

Abstract In this work, a facile and effective method which can significantly improve the flux-pinning performance of YBCO films was reported. YBCO/CeO 2 composite films were prepared on LaAlO 3 (LAO) single crystal substrates through a fluorine-free sol-gel approach with a certain amount of ceria addition. During the nucleation and growth of YBCO films, CeO 2 reacted with the barium-contained phase in YBCO precursors to generate the nanosized BaCeO 3 phase and thus the redundant Y 2 O 3 and CuO phases remained, leading to the wrong stacking of Cu atoms to form the stacking faults of Cu-O planes, which has been demonstrated by XRD, TEM, SEM and EDS results. The variation of critical current density (J c) and flux-pinning force (F p) with the percentage of ceria addition was investigated, and the results show that YBCO film with the amount of 5 mol% of ceria addition exhibits the highest J c and the strongest F p at the same temperature and applied magnetic fields. In addition, the stacking faults effectively reduced the degree of dependency of J c of YBCO film on the applied magnetic field especially at low temperature. [ABSTRACT FROM AUTHOR]

In this work, Zr-doped CeO 2 (Ce 1-x Zr x O 2 , CZO) films with (001) preferential orientation were fabricated on biaxially textured NiW alloy substrates by using a novel sol-gel method. The precursor solutions were synthesized through a newly developed process using common inorganic metal salts of Zr and Ce as the starting materials instead of organic salts. The influence of annealing temperature and the Ce/Zr mole ratio in the precursor solutions on the growth texture of CZO films was investigated. The precursor solutions with the concentration of 0.3 mol/L were coated on the Ni5W substrates using a dip-coating method and then heat-treated at 1050 °C for an hour under a reducing atmosphere of high-purity Ar with 5 vol% H 2 . The CZO thin films show excellent c-axis preferential orientation when the content of Zr in CZO thin film is less than 40%. The full width of half maximum of the phi scan of (111) reflection and omega scan of (200) reflection of CZO films is as low as the value of about 5° and 6°, respectively. Moreover, it is found that the inside of CZO thin film exhibits quite dense and uniform without cracks and porosity with the aid of the scanning transmission electron microscopy analysis by which the epitaxial growth relationship of (220) CZO // (200) NiW between CZO and NiW is simultaneously confirmed. Finally, highly (00  l )-oriented YBCO film with good superconducting properties was deposited on CZO buffered NiW substrate. The above results indicate that the CZO film is a quite promising candidate of single buffer layer architecture for YBCO coated conductor. [ABSTRACT FROM AUTHOR]

In this work, YBCO films were epitaxially grown on Ce 1−x Zr x O 2 (CZO) buffered yttria stabilized zirconia (YSZ) single crystal substrates through a fluorine-free sol-gel process. The influence of two different CZO buffer architectures on the microstructure and superconducting properties of YBCO films was investigated. According to XRD results in combination with (S)TEM analysis, it was confirmed that YBCO film grown on the gradient CZO buffer layer (CZO-G) exhibits better in-plane and out-of-plane texture than YBCO film deposited on the uniform CZO buffer layer (CZO-20). And besides, the superconducting performances especially the current-carrying capacity under magnetic field of the former was much higher than that of the latter, which means that the enhanced flux pinning force will be presented in YBCO film on CZO-G buffer layer. The maximum pinning force of the YBCO film grown on CZO-G buffer architecture is up to 17.67 GN/m 3 @ 65 K. HR-STEM analysis shows that the stacking faults within YBCO matrix gave rise to the considerable nanoscale lattice-strains which may suppress the formation of Copper pairs and produce nanoscale non-superconducting regions served as pinning centers to significantly improve the flux pinning performance of YBCO film. Given the above, it has been implied that high-performance YBCO coated conductor can be developed by using a compositional gradient Ce 1−x Zr x O 2 films as buffer architecture. [ABSTRACT FROM AUTHOR]