Two step synthesis of TlBa₂Ca₂Cu₃O_x films on Ag substrates by spray pyrolysis of metal-acetylacetonates

A two-step synthesis process was performed to obtain TlBa₂Ca₂Cu₃O_x (Tl-1223) superconductor films. The synthesized films were obtained under different thallium diffusion conditions in a two-zone furnace precursor films were deposited at 550°C on silver substrates using the spray pyrolysis technique from acetylacetonates (2, 4-pentanedionates) as reagents. Second, a thallium diffusion process is carried out to incorporate Tl in the films. For this task Tl₂O₃ pellets, as a Tl source, were used at 750°C. Different oxygen flow rates at atmospheric pressure were used in order to get the thallous oxide p(Tl₂O) partial pressure in the range of 6:9x10^-4 to 6.1x10^-2 atm. The Tl-1223 phase was obtained in all cases, though for a low p(Tl₂O), the films presented the BaCuO₂ phase mixed with the Tl-1223 one. Critical temperature (TC) values for these films were in the range of 90 to 102 K.