Two step synthesis of TlBa$_{2}$Ca$_{2}$Cu$_{3}$O$_{x}$ films on Ag substrates by spray pyrolysis of metal-acetylacetonates

Abstract

A two-step synthesis process was performed to obtain TlBa$_{2}$Ca$_{2}$Cu$_{3}$O$_{x}$ (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$^\circ$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 Tl$_{2}$O$_{3}$ pellets, as a Tl source, were used at 750$^\circ$C. Different oxygen flow rates at atmospheric pressure were used in order to get the thallous oxide p(Tl$_{2}$O) partial pressure in the range of $6.9{\times}10^{ - 4 }$ to $6.1{\times}10^{ - 2}$ atm. The Tl-1223 phase was obtained in all cases, though for a low p(Tl$_{2}$O), the films presented the BaCuO$_{2}$ phase mixed with the Tl-1223 one. Critical temperature (T$_{C})$ values for these films were in the range of 90 to 102 K.