MELT PROCESSING OF ALKALI ELEMENT DOPED BI2SR2CACU2O8

The effect of alkali element doping on the superconducting properties of the Bi-Sr-Ca-Cu-O system has been investigated. It was found that a T(c) of 94 K and T0 of 90 K in alkali element doped Bi2Sr2CaCu2O8 were achieved through the use of a melt-processing technique. XRD, SEM and EDS examinations showed that the samples did not contain the high-T(c) phase Bi2Sr2Ca2Cu3O10. It is argued that the mechanism for the enhancement for the T(c) through alkali element doping derives from a fluxing action, which provides a fast diffusion path for Ca and Cu to the superconducting phase, resulting in the desirable stoichiometry of Bi2Sr2CaCu2O8. On the other hand, the substitution of alkali elements in the superconducting phase may give rise to a reducing effect of the oxygen content, leading to the enhancement of the T(c). The latter mechanism may be compounded with the fluxing action. Alkali elements were found to be excellent sintering aids for processing Bi-based superconductors since they enhance the T(c) and promote grain growth and grain aligment in the bulk materials.