A New Family of 2223-Type Superconductors, (Tl1-xHgx)2Sr2Ca2Cu3Oy Synthesized Under High Pressure
We have synthesized new Ba-free Tl-based superconductor (Tl1-x Hg x )2Sr2Ca2Cu3Oy using high-pressure high-temperature technique. These compounds are chemically and structurally stabilized by partial substitution of Hg for T1. While Hg-free compound is multi-phased, Hg-doped compounds (x = 0.35–0.65) were nearly single phased and found to be superconducting with T c ’s of 80–103 K. Electron diffraction and transimission electron microscope observations have revealed a body centered tetragonal unit cell isostructural with Ba-containing Tl-2223 phase with the Ba-sites occupied by Sr. From structural refinements of the XRD data for x = 0.35, it was found that Sr and Cu sites are fully occupied, Whereas the Tl-site and the Ca-site are partially occupied by Cu and Tl, respectively. Reducing treatments in Ar/H2 atmosphere were found to be effective in enhancing T c up to 116 K for x = 0.35.
KeywordsNominal Composition Longe Annealing Time Tetragonal Unit Cell Refined Lattice Parameter Special Coordination Fund
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