Influence of the reaction conditions on the formation of Tl(Re)-Ba-Ca-Cu-O superconducting thin films by thallination in open system

Abstract

Rhenium avoids air degradation of the target as well as of precursor thin films during the preparation of high temperature Tl-based superconductors. Addition of Re has been used during synthesis of oriented Tl(Re)-Ba-Ca-Cu-O films. High temperature superconducting Tlbased thin films were prepared by a two step method combining RF magnetron sputtering and ex-situ thallination. Precursors with a composition of Re 0.1 Ba 2 Ca 2 Cu 3 O x were deposited on a CeO 2 buffered R-plane sapphire substrate. The sputtered films were prepared at room temperature in an Ar atmosphere. The thallination of the precursor films was performed in a one zone configuration, where both the pellet and precursor film were kept at the same temperature. The thallination temperature varied in the range of 850 -880• C and samples were held for 30, 45 and 60 min at this temperature in a flowing oxygen atmosphere. Besides Tl-2212, X-ray diffraction reveals the possibility of also preparing the Tl-2223 phase, which was until now not reported in a Re doped form.