(Bi_<2.1-x>Pb_x)Sr_<2.0>Ca_<0.9>Y_<0.1>Cu_<2.0>O_yにおけるT_c, J_cのPb置換量, 酸素量依存

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The purpose of this paper is to interpret the enhancement of T_c and J_c by the replacement of cations and the change of excess oxygen content for Bi-rich 2212 system, (Bi_<2.1-x>Pb_x)Sr_<2.0>(Ca_<0.9>Y_<0.1>)Cu_<2.0>O_y, especially in overdoping region. The bulk samples were prepared by coprecipitation method. In bulk samples, the c-axis and Bi + Pb valence decrease and Cu valence increases with increasing Pb content, x. T_<c(zero)> increases with increasing x in the single phase region. On the other hand, the c-axis and Cu valence increase and Bi + Pb valence slightly increases with increasing excess oxygen content, ⊿y. An optimum excess oxygen content which brought a maximum T_<c(zero)> was found to exist at each Pb content. Furthermore, in order to elucidate the effects of metal substitution and oxygen content on J_c of the Bi2212 system, the films with the same metal compositions were prepared by the spin coating pyrolysis method. From the results of highly orientated thin films, J_c increases with increasing excess oxygen content, ⊿y, in the oxygen doping region, while it increases or keeps constant in the oxygen overdoping region. According to the results, the metal composition and oxygen content are very important for obtaining the highest T_c and J_c.
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2001-11-01