Superconducting tapes with critical current density of 104 A/cm2 at 77 K and zero magnetic field

This paper reports on critical current density above 104 A/cm2 at both YBa2Cu3O6.8 (YBCO) thin films on metallic substrates and Bi-based superconducting films on silver tapes. A transition buffer, consisting of sub-buffers deposited at different temperatures, was used to enhance the crystallinity and the transport properties of YBCO films on metallic substrates. YBCO films were fabricated, using in-situ laser deposition, and they were strongly c-axis oriented. Critical temperature of 87 K and critical current density of 3 x 104 A/cm2 at 77 K were obtained for a 0.5 μm-thick YBCO film. Also, the magnetic field dependence of Jc could be increased by using Pt-coated metallic substrates. For 10 ∼ 20 μm-thick Bi-based superconducting tape, by using brush-on technique and heat treatment, critical current of 104 A/cm2 at 77 K was obtained