The influence of the reaction conditions on the formation of Tl-2223 superconducting films deposited by spray pyrolysis

Abstract Thick superconducting Tl-based films ( d ≅1 μm) have been prepared on LaAlO 3 substrate by a two-step process involving the deposition of the Ba–Ca–Cu–O precursor by spray pyrolysis and ex situ thallination. The influence of the different reaction conditions (temperature, thallination time and thallium content in the source pellet) on the composition of the film was investigated by X-ray measurement. Films with different multiphase composition (Tl-2223, Tl-1223, intergrowth phases, Tl-2212) were obtained. A thallination temperature of 900 °C was necessary for Tl-2212→Tl-2223 transformation. The thallium concentration during the annealing had to be optimized. The zero resistance critical temperatures T C0 of the films were in the range of 100–117,5 K, the obtained films were biaxially textured with plate-like grains morphology.