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In this work we present a systematic study of the Mn influence superconducting properties. Attempts have been made to identify the optimum inclusion of MnO in BiSrCaCuO superconductors. The phase formation, texture and grain alignments were analysed by X-ray diffraction, scanning electron microscopy, energy dispersive spectrometry (SEM, EDS) and electrical resistivity. It was found that Mn addition has affected the formation of the desired Bi-2212 phase and the microstructure of these samples thereby influencing on the resistivity. The resistivity of all the BiSrMnCaCuO samples shows metallic behaviour. It reveals that, 4 wt% composite exhibits a better superconducting property in comparison with pure BSCCO. It has been observed that Mn residing at the grain boundary of BSCCO matrix influences the tailing region with having significant change in the critical temperature. The microstructures observed by SEM indicate segregation of an additional phase. The EDS revealed that this phase is stoichiometric. The results show that the doping leads to a reduction of cell volume as well as the c axis. [ABSTRACT FROM AUTHOR]

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]