Development of YBa2Cu3O7−x superconducting films on (100) SrTiO3 and (110) Ag substrates by chemical spray pyrolysis

Abstract

YBa₂Cu₃O_7−x films have been deposited using spray pyrolysis on (100) SrTiO₃, (110) Ag single crystals and {110}<011> textured Ag tapes. An extended and systematic study on the optimization of composition, carrying gas flow, deposition temperature as well as annealing time was performed. It was found that these parameters are strongly correlated and affect the morphology, orientation and superconducting properties of the YBCO films. For the Y-123 film deposited on Ag single crystals, the T_c onset was at 90 K and a transport J_c value of around 10⁴ A cm⁻² (at 77 K) was observed. On SrTiO₃ substrates, an in-plane orientation FWHM value of 0.70° was measured for the (102) pole figure. As-grown films already exhibit J_c values of 10⁴ A cm⁻², thus indicating that the correct structure is already formed during deposition. It was found that the temperature gradient in the pyrolysis zone played a fundamental role during the deposition. After modification of this heat gradient by adding a metallic susceptor, a noticeable improvement in the properties of the films was obtained. The films exhibited a T_c onset of 91 K (ΔT_c = 1.5 K), while the J_c value at 77 K in self-field approached 10⁵ A cm⁻². According to our analysis, we find a 40 × 40 μm area in our best film where the critical current density reaches 5 × 10⁶ A cm⁻².