Preparation and Superconducting Properties of (Tl,Pb)-Based Compounds with 1234-Type Structure

초록

(Tl(1-x) Pb (x) )(Sr(2-y) Ba (y) )Ca(3)Cu(4)O (z) samples were synthesized by using a two-step solid state reaction method and examined with respect to the (Tl,Pb)-1234 phase formation and superconducting properties. Samples were prepared from various starting compositions of 0a parts per thousand currency signxa parts per thousand currency sign0.5 and 0.4a parts per thousand currency signya parts per thousand currency sign2.0. Nearly single-phased samples were obtained for (Tl(0.8)Pb(0.2))(Sr(2-y) Ba (y) )Ca(3)Cu(4)O (z) (1.0a parts per thousand currency signya parts per thousand currency sign1.25) and (Tl(1-x) Pb (x) )(SrBa)Ca(3)Cu(4)O (z) (0.15a parts per thousand currency signya parts per thousand currency sign0.35). We have found that both the partial substitution of Ba for Sr and the partial substitution of Pb for Tl are effective for the formation of the Tl-1234 phase. Bulk superconductivity with a T (c) value of 106 K is observed in the (Tl(0.7)Pb(0.3))(SrBa)Ca(3)Cu(4)O (z) sample.

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