Bi_<2.20-z>Pb_zSr_<1.86>Ca_<2.03>Y_<0.05>Cu_<2.86>O_y超伝導酸化物におけるT_c,J_cのPb置換量及び酸素量依存

概要

論文の詳細を見る
The purpose of this paper is to interpret the enhancement of T_c and J_c by the replacement of cations and changing the excess oxygen content for Bi-2223 system by the replacement of Bi and Ca by Pb and Y, respectively, that is Bi_<2.20>-_zPb_zSr<1.86>Ca_<2.03>Y_<0.05>Cu_<2.86>O_y. The relations between lattice constant, average valences of Bi + Pb and Cu, excess oxygen content and superconducting characteristics have been studied by changing Pb substitution content, and annealing treatment. Bulk samples were prepared by the coprecipitation method. Furthermore, in order to elucidate the effect of metal substitution and oxygen content on J_c of the Bi-2223 system, films which have the same metal composition of the bulk, were prepared on MgO (100) single crystal substrate by the spin coating-pyrolysis method. Measurements of J_c and T_c were carried out on highly oriented films of Bi-2223 phase with changing Pb content and oxygen content: T_c (zero) experienced a maximum at Pb content, z = 0.50 (nominal composition), and T_c (zero) decreased with increasing z in the region z > 0.50. On the other hand, J_c also showed a maximum at z = 0.50, but it was constant with increasing z in the region z > 0.50. Oxygen underdoped and over-doped regions, and the highest T_c (zero) and J_c were obtained upon adjusting the optimum excess oxygen con-tent, by changing Pb content and annealing treatment.
2005-02-01