Pb content and oxygen content dependences of T-c and J(c) for (Bi2.1-xPbx)Sr2.0Ca0.9Y0.1Co2.0Oy

The purpose of this paper is to interpret the enhancement of T-c and J(c) b y the replacement of cations and the change of excess oxygen content for Bi -rich 2212 system, (Bi2.1-xPbx) Sr-2.0(Ca0.9Y0.1)Cu2.0Oy, especially in ove rdoping region. The bulk samples were prepared by coprecipitation method. I n bulk samples, the c-axis and Bi+Pb valence decrease and Cu valence increa ses 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 incr ease and Bi+Pb valence slightly increases with increasing excess oxygen con tent, Deltay. An optimum excess oxygen content which brought a maximum T-c( zero) was found to exist at each Pb content. Furthermore, in order to eluci date the effects of metal substitution and oxygen content on J(c) of the Bi 2212 system, the films with the same metal compositions were prepared by th e spin coating pyrolysis method. From the results of highly orientated thin films, J(c) increases with increasing excess oxygen content, Deltay, in th e oxygen doping region, while it increases or keeps constant in the oxygen overdoping region. According to the results, the metal composition and oxyg en content are very important for obtaining the highest T-c and J(c).