Sr-doping for promoted high-Tc BPSCCO superconductors

Nearly single phase superconducting samples of the general formula (Bi/Pb)(2)(Sr2-xCax)(2)Cu3O10 were prepared by the usual high temperature solid state reaction technique and ceramic procedures. The prepared sample with x = 0.6, with optimally nominal oxygen content (over doped) shows T-c of 107 K. The increase in T-c is also accompanied by an increase in the room temperature c-axis length. The crystal structure of the sample was determined by Cu-K, X-ray diffractometry. This crystal belongs to a tetragonal system and has a space group of 14/mmm with a = 3 6732 Angstrom and c = 34.3176 Angstrom. The TGA and DTA thermal analyses on the green samples included steps of thermal decomposition of CuCO3 (300-400 degreesC). CaCO3 (660-710 degreesC), SrCO3 (710-800 degreesC) and finally to the high temperature solid state formation of superconductive phase at 820 degreesC Finally a proposed crystalline structure symbol was put forward. (C) 2002 Elsevier Science B.V. All rights reserved.