Growth of TlBa₂Ca₂Cu₃O_9-y superconducting films with local biaxial alignment extending up to 5 mm on Ag substrates using a spray-pyrolysis technique

We report on the superconducting properties of TlBa₂Ca₂Cu₃O_9-y (Tl-1223) thick films grown on smooth and rough Ag substrates. Thallium-free precursor films of the type Ba₂Ca₂Cu₃Ag_0.37O₇ were deposited on Ag substrates using a spray-pyrolysis technique followed by post-thallination in a two-zone furnace. X-ray diffraction (XRD) results showed the presence of c-axis aligned Tl-1223 films and some degree of local in-plane texture (often referred to as a colony microstructure). The microstructure of the Ag surface dictates the growth behavior of Tl-1223 films. The transport critical-current densities (J_c) for Tl-1223 films grown on smooth and rough Ag substrates were ∼ 65,000 A/cm² and ∼ 37,000 A/cm², respectively, at 77 K and zero field. The films grown on smooth Ag substrates were strongly linked and had good in-field properties with a J_c value of ∼ 10⁴ A/cm² at 77 K and 0.5 T.