Effect of high-pressure compaction on the properties of Tl2Ba2CaCu2OyFx (x = 0, 0.1, 0.2) ceramics

Tl₂Ba₂CaCu₂O _y F _x (x = 0, 0.1, 0.2) high-T _c ceramics have been prepared using high-pressure compaction. Their phase composition and electrical properties have been studied, and their crystal structure have been refined by the Rietveld method. The results demonstrate that high-pressure compaction makes it possible to reduce the synthesis temperature of Tl₂Ba₂CaCu₂O _y F _x ceramics from 840 to 825°C and to obtain more structurally perfect materials, with a higher density and narrower superconducting transition (4–7 K). With increasing fluorine content, the carrier (hole) concentration in the Tl₂Ba₂CaCu₂O _y F _x ceramics decreases, leading to changes in their superconducting transition temperature. The Cu-Cu bond distance and CuO₂-Ba interplanar spacing are proposed as key parameters for T _c control. Original Russian Text ? A.I. Akimov, S.A. Lebedev, T.V. Tarasevich, O.V. Ignatenko, 2008, published in Neorganicheskie Materialy, 2008, Vol. 44, No. 3, pp. 375–384.