Temperature-Modulated Growth of MOCVD-Derived YBa₂Cu₃O_7−x Films on IBAD-MgO Templates

Thecost-effective and environment-friendly template of LaMnO₃/epi-MgO/ion beam-assisted deposited (IBAD-)MgO/solution deposition planarized (SDP) Y₂O₃/Hastelloy tape was used as the substrate, on which the technique of metal organic chemical vapor deposition (MOCVD) has been applied to depositing 1.2- μm-thick YBa₂Cu₃O_7−x(YBCO) films by modulating the substrate temperature ranging from 750 to 850 ^∘C. The effects of substrate temperature on the preferential orientation, textures, surface morphology, and performance of the YBCO films were systematically investigated. X-ray diffraction and scanning electron microscope revealed that as substrate temperature increased from 750 to 810 ^∘C, the orientation of YBCO films was transferred from the a-axis to the c-axis; meanwhile, the textures were improved and the films became denser. However, as the substrate temperature rose above 810 ^∘C, the composition distributions and textures of YBCO films degraded quickly, and the films were barium-poor with CuYO₂ impurity arising, of which all negatively affected the critical current density (J_c) of YBCO films. Around 810 ^∘C, the YBCO film was of the best crystallization and microstructure as well as highly epitaxial growth, leading to the highest J_cof 1.8 MA/cm ² at 77 K and self-field.