Effects of excess oxygen content on the hole-carrying CuO2-layers in Tl-2(Ba1-xSrx)(2)Ca(2)Cu(3)Oy superconducting oxides

摘要

The effects of oxygen doping on the hole-carrying CuO2-layers in Tl-2(Ba1-xSrx)(2)Ca2Cu3Oy were studied by combined chemical and valence analysis, T-c measurements and neutron diffraction. The highest T-c is characterized by an optimal excess oxygen content, Deltay, dichotomizing the under- and over-doped regions for each Sr concentration. While the average TI valence is close to 3.0 and independent of Deltay, the average Cu valence shows a linear dependence with Deltay. An increase of the flatness of the CuO2 plane, characterized by the O(2)-Cu(2)-O(2) bond angle of similar to176degrees, was observed at the optimal Deltay. (C) 2004 Elsevier Ltd. All rights reserved.