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Tl-based superconducting films prepared by aerosol spray deposition and thallinated in an open system

100%

Matkovičová Z., Štrbík V., Plesch G., Valeriánová M., Dujavová A.

Open Physics

2007

vol. 5

issue 3

398-404

Superconducting Tl-based films were prepared on a LaAlO3 single crystal substrate. Spray pyrolysis of Ba, Ca and Cu nitrate solutions was used for deposition of the precursor films. They were subsequently ex-situ thallinated in flowing oxygen (open system). While the superconducting Tl-2212 phase formed at an annealing temperature of 880°C, thallination at 900°C led to the formation of a Tl-2223 /Tl-2212 mixture. The amount of Tl-2223 increased with prolonged thallination, whereas the Tl-2212 phase progressively disappeared. Films prepared in such a manner were c-oriented and contained only low amounts of non-superconducting impurities. The resulting samples were characterized by XRD and SEM and their T C values were determined by resistive four-point measurements. They showed critical temperatures in the range of T ON = 125–135 K, T C0 = 91–93 K. Differences between the composition and properties of the obtained films and those thallinated in closed systems under 50 kPa of oxygen are discussed in this paper. Results show that the Tl-2212 → Tl-2223 transformation proceeds at a slower rate under flowing oxygen than in a closed system.

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

86%

Dujavová A., Valeriánová M., Štrbík V., Matkovičová Z., Plesch G., Kostič I.

Open Physics

2007

vol. 5

issue 2

229-235

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 Tl-based thin films were prepared by a two step method combining RF magnetron sputtering and ex-situ thallination. Precursors with a composition of Re0.1Ba2Ca2Cu3Ox were deposited on a CeO2 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.

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2 Open Physics

2 2007

2 Dujavová A.

2 Matkovičová Z.

2 Plesch G.

2 Valeriánová M.

2 Štrbík V.

1 Kostič I.

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Tl-based superconducting films prepared by aerosol spray deposition and thallinated in an open system

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