High Temperature Superconductors from a Pure Glassy Phase

B. K. Chaudhuri

《Chinese Journal of Physics》 38卷2S期 (2000/04) Pp. 211-224

並列摘要

Homogenous (Bi3Pb)Sr3Ca3(Cu4¡ nMn)Ox type glassy precursors (M = Li, K, Cr, Mn, Zn, Ti, Ag; and n = 0-0.5) show high Tc superconducting behavior when they are annealed at 840℃ for 24 hrs in air. The superconducting behavior of a typical Cr doped sample is only discussed in this paper. Samples doped with other atoms also behave similarly. All these glasses contain nanocrystalline particles or clusters which grows into the superconducting or other phases by annealing. Single phase high Tc superconductors are obtained from the glasses having nanocrystals size ＜ 20 nm. The suppression of transition temperature supports the pairbreaking mechanism of Abrikosov and Gor'kov. Depending on the measuring temperature, both positive and negative values of the Seebeck coefficients (S) are exhibited by the annealed superconducting samples. Interestingly, small positive peaks were shown by the thermoelectric power (TEP) data of all the doped samples just above Tc. This peak was considered to be associated with the phonon-drag effect. Similar behavior is also exhibited by the correspondingsuperconductors doped with Mn, Fe and Ti. The linear part of the temperature vs. TEP data (above Tc) can be well fitted with the two band model.