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Abstract: The influence of Ag, Mg, and Pr additions and co-additions on microstructure and phase formation of Bi2Sr2CaCu2O8+d (Bi2212) system is investigated. Polycrystalline Bi2212 samples were synthesized in air by solid state reaction method. Phase analysis, micro structural observations and magnetic properties were carried out by X-ray diffraction (XRD), scanning electron microscopy (SEM) and A.C. susceptibility measurements respectively. XRD results reveal two main phases (Bi-2201 and Bi2212). SEM photographs show that the substitution by Ag, Mg or Pr affects the mechanism of the grains growth. The undoped sample has a critical temperature Tc of 65 K while in the Mg and Ag containing compounds the Tc is 77 K and 75 K respectively. The Pr containing compound exhibits no superconductivity. A valence of the Pr ion higher than 3+ in the lattice supports the holefilling mechanism of the suppression of superconductivity. [Copyright &y& Elsevier]

Abstract: Since the discovery of the high temperature superconductivity in the Bi-Sr-Ca-Cu-O system , many investigations have focused on it to understand its properties and to improve them. Belonging to this system, the (Bi-2212) phase has been widely studied in the recent years in order to understand, by various kinds of substitution, the relation between the structure and the superconductivity. Most of these substitutions have concerned the Cu site in the superconducting layer . Among these, as showed by G. Ilonca et al., the substitution by Fe kills the superconductivity at a lower concentration than Ni. At our knowledge, nothing has been made when there is in the same time a substitution by lead (Pb) on the Bi site. For that purpose samples of with –0.06, have been prepared using the solid state reaction technique. The samples have been characterized by X-ray diffraction (XRD) and scanning electron microsopy (SEM). Structural analysis shows the influence of the Fe doping on the crystalline lattice structure of the samples. [Copyright &y& Elsevier]