Preparation and superconducting properties of Y-Ba-Cu-O films on oxide polycrystalline substrates by chemical vapour deposition

Y-Ba-Cu-O superconducting films were prepared on Y₂O ₃-stabilized ZrO₂(YSZ), MgO and Al₂O ₃ polycrystalline substrates by chemical vapour deposition using beta -diketone metal chelates as sources. The c-axis of YBa₂Cu ₃O_y was mainly oriented perpendicular to the plane of the films obtained above 800 degrees C. The films deposited on YSZ and MgO at 850 degrees C showed zero resistivity at 90 K and 87 K, respectively. The superconducting transition temperature of 71 K was the highest among the transition temperatures of the films deposited on Al₂O₃. The critical current density (J_c) of the film on YSZ was 8.0*10³ A cm^-2 and that of the film on MgO was 1.0*10⁴ A cm^-2 at 77.3 K and 0 T. J_c measured at 77.3 K under an applied magnetic field of 15 T parallel to the film planes was 44 A cm^-2 for the film on YSZ and 27 A cm^-2 for the film on MgO. The temperature gradients of the upper critical field (-dB_c2/dT) determined by the definition of zero resistivity for upper critical field (-dB_c2/dT) determined by the definition of zero resistivity for the film prepared on the YSZ substrate were 4.7 T K^-1 and 1.0 T K^-1 when the magnetic field was parallel and perpendicular to the film plane, respectively.