| Among Bi-base superconductors described as Bi2Si2Can-1CunOy (Bi-22(n-l)n;n=l, 2, and 3), Bi-2223 is one of the most promising materials for application to wires and tapes at 77K, in comparison with other cuprate superconductors. It has high critical temperature 110K. However, the critical current density of PIT( power in tube )Bi-2223 tapes has not been significantly improved. this originates from the fact that Bi-2223 tapes has poor flux pinning property and irreversibility field (Hirr).Flux-line interacts with pinning centres because the superconducting properties of the latter are different from those of the bulk of the superconducter. The strength of the interaction is a function of the magnitude of this difference the difference may be small, and manifest itself as a difference in critical temperature, critical field, or Ginsberg-Landauκ. The difference may be large, as is the case when the pinning centre is non-superconducting. The largest difference, and hence the strongest pinning, arises when the pinning centre is ferromagnetic. Of all the various possibilities, only two are believed responsible for flux-pinning in the majority of commercial superconducting materials. Those are (i) small differences inκ, arising from changes in the normal state resistivity, due to composition fluctuations, non-uniform distributions of dislocations of martensite transformation, and (ii) non-superconducting particles, which may be normal metal, insulator or void. The two types of pinning centres named as '△κpinning' and 'normal pinning'.The method of systematic creation of point defects in the OuO2 planes of the high-temperatures superconductors by replacing the Cu atoms by other 3d elements in a useful tool for probing parameters essential for the superconductivity when point defects are introduced into the CuO2 planes, for example, can give information about the interaction of the charge carriers with the impurity. There is experimental evidence that impurities in the OuO2 planes, even if they are nonmagnetic, can change the magnetism of the neighboring Cu spins drastically by inducing local Cuy moments, or, in the holon-spinon language, by causing the condensation of a spinon. The superconductivity of the high-Tc cuprates is generally strongly suppressed by substitutional elements in the CuO2 planes. In the system (La1-xSrx)2CuO4, about 4 at.% of substitution in the Cu position is sufficient to quench the superconductivity. In n-type superconductors like (Pr1-xCex)2CuO4, the influence is even stronger, and Ni and Fe concentrations below 1at.% suppress the superconductivity completely.In this paper we presented an effective method of producing pinning centers which lead to an enhancement of the pinning in the Bi-2223 tapes via partial substitution of Fe for Cu. The effect of Fe-doping on Cu sites on the flux pinning of Bi-2223/Ag tapes is investigated. The results showed that is similar as that of Cr-doping by M.H Pu .It is found that Fe-doping can induce a large amount of Fe-ion-defects in the superconducting layers of Bi-2223. With proper Fe-doping, the dispersed Fe-ion-defects similarly act as point pinning centers of normal phase at liquid nitrogen temperature, and enhance the flux pinning in Bi-2223/Ag tapes drastically. In the Fe-doped tapes, the favorite Fe-doping amount is also about 0.001 per formula unit of Bi-2223, Similar to the tapes with Cr-doping. However, when the tapes are doped with exceeded level, Fe-ion-defects and Fe-ion-defects will slightly accumulate, At this condition, the weak superconducting regions will overlapped so that the effects of more flux pinning sites is not relevant any more.
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