Kinetics studies for the formation of Tl-1223 films prepared by spray pyrolysis

TlBa₂Ca₂Cu₃O₉ (Tl-1223) superconducting thick films with J_c as high as 0.8 MA/cm² have been recently prepared in a two step process which involves (i) the deposition of the “Ba₂Ca₂Cu₃O₇” precursor on heated LaAlO₃ substrates by spray pyrolysis and (ii) an ex-situ thallination treatment, following a procedure already applied for bulk samples. The kinetics for the formation of the superconducting phase has been studied to determine the optimum processing temperature and time for better control of the grain growth and the superconducting properties. The data analysis, based on a diffusion model, leads to an estimated value for the activation energy E_a of 161 kJ/mol. The effect of fluorine addition on the film morphology and microstructure is also studied. It is found that both c-axis orientation (Δω = 0.34°) and in-plane texture (Δϕ =0.43°) are significantly improved with respect to F-free films.