Bulk Superconductivity of the (Tl_<0.5>Bi_<0.5>)(Ca_<1-x>Y_x)Sr_2Cu_2O_y System

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A family of Tl_<0.5>Bi_<0.5>)(Ca_<1-x>Y_x)Sr_2Cu_2O_y compounds with x=0, 0.1, 0.2, 0.3, 0.5 and 0.7 were studied systematically. The major phase (above 90%) of all sintered samples was identified as (Tl, Pb)CaSr_2Cu_2O_y, an isostructure of the 1122 phase. A maximum T_c_<zero> up to 102 K was achieved at x=0.2, and semiconducting behavior was found at x=0.7. The magnetization measurement is consistent with the resistance data observed. The c-axis of a unit cell contracted significantly and monotonically as the Y substitution increased. It appears that the reduction of the interlayer distance as well as the excess positive charge introduced by substitution played an important role on superconductivity; the difference from a similar Y-substituted Bi_2(Ca_<1-x>Y_x)Sr_2Cu_2O_y system was discussed.
社団法人応用物理学会の論文
1989-09-20