Preparation of (Tl,Bi)(Ba0.4,Sr1.6)Ca2Cu3O9 thick films epitaxially grown on LaAlO3 (100) substrates by a sol-gel process

We report on the preparation of 5 μm thick (Tl,Bi)(Ba_0.4,Sr_1.6)Ca₂Cu₃O₉ ((Tl,Bi)-1223) high T_c films by a modified sol-gel (Pechini) process. The process was performed by the preparation of a gel containing the metallic atoms, the coating of the substrates with the gel, the pyrolisis of the gel, and a post annealing process, without an additional thallium oxide vapour source. X-ray diffraction patterns (θ - 2θ scans) showed that the thick films prepared on LaAlO₃(100) substrates consisted mainly of the (Tl,Bi)-1223 phase, with high c axis orientation, and φ scans revealed epitaxial film growth. EDX measurements showed a composition in good agreement with the (Tl,Bi)-1223 phase. Superconductivity was reached with T_c values up to 102 K.