Structural characterisation of high temperature superconductors by neutron profile refinement technique

The structures of a variety of high-Tc superconductors in the Y-Ba-Cu-O, Tl-Ba-Ca-Cu-O and Bi-Sr-Ca-Cu-O systems have been investigated by neutron profile refinement technique using the high flux Dhruva reactor. These investigations have led to the observation of some novel structural features including the ageing effects, the cationic scrambling effects, the oxygen-pairing effects with associated structural changes and their correlations with Tc. The advantages of neutron Rietveld refinement technique for structural characterisation of materials invloving lighter atoms, particularly the high-Tc ceramics are illustrated. The consequences of Y and Pb substitution on the oxygen stoichiometry and structure of Bi-Sr-Ca-Cu-O superconductors are reviewed. (author). 19 refs., 12 figs