The study of critical current density of superconducting thallium oxide films from spray-deposited precursors

Spray deposition is a promising and economic approach for fabricating high-temperature superconducting films for the Tl-oxide superconductors. The Tl-oxides provide the potential for operation at 77 K in practical magnetic fields of 3–5 T, which has been demonstrated by measurements on the irreversibility behavior of the Tl-1223 single layer compound with Bi and Sr substitution. In this report, we present the preparation and characterization of Tl0.78Bi0.22Sr1.6Ba0.4Ca2Cu3O9 superconducting films fabricated from spray-deposited Tl-free, Ag-containing and Cu-rich precursors and reacted with thallium vapor using a two-step crucible process at 650°C/815°C in flowing argon for only 10/10 min. An epitaxial superconducting film was synthesized successfully and critical current densities of 8×105 A/cm2 at 77 K in zero-field were obtained with excellent in-field performance.