Correlation between the Tl concentration depth profiles and the thallination time in Tl-Ba-Ca-Cu-O superconducting films

The elemental composition and depth profiles of superconducting Tl-Ba-Ca-Cu-O (TBCCO) films deposited on yttrium-stabilized zirconia (YSZ) substrates were studied by IBA techniques such as RBS and NRA. The TBCCO films were prepared by annealing in thallium vapour a series of spray deposited Ba2Ca2Cu3Ox precursor films with crude Tl2Ba2Ca2Cu3Ox pellets at 850C for various times of thallination in s single-zone reaction chamber. Synthesized TBCCO films, 3?4 ?m thick, were characterized by resistivity and XRD measurements. The zero resistance Tc values ranged from 87 to 97 K, depending on the time of thallination. IBA studies revealed a correlation between the Tl concentration depth profiles and the thallination time. The highest Tc value, 97 K, was obtained after a relatively short thallination time of 5 min, leading also to the best crystallographic orientation. The physical implications of these results are discussed.