Characteristics of high Tc superconducting thin films prepared by chemical vapor deposition

Superconducting YBa₂Cu₃O_7-x thin films were prepared at 750-840°C by chemical vapor deposition (CVD) using beta-diketonate chelates on single-crystal SrTiO₃, MgO substrates, and metal substrates. The best films on single-crystal MgO had zero-resistance T_c at 89 K and J_c above 3.6×10⁴ A/cm² (at 77.3 K, 0 T). On SrTiO₃, the best films had T_c at 92.5 K and J_c above 2.0×10⁵ A/cm². X-ray diffraction confirmed the existence of orthorhombic crystal structures having c-axis orientation. The magnetic field dependence of J_c of the YBCO film was measured at 77.3 K. J_c depends on the angle between the direction of the applied field and that of the c-axis of YBCO. Superconducting tapes that are 10-cm long were obtained by CVD using Ni-based alloy as a substrate. These tapes had the crystal structures of YBa₂Cu₃O_7-x (110)-oriented and T_c at 84.5 K. The strain dependence of J _c was measured. Bending strain of up to 0.08% did not reduce J_c