The influence of sintering and Sb content on the formation of high temperature superconducting phase in Bi(Pb)-Sr-Ca-Cu-O system

Six different compositions in (Bi1.5Pb0.5-xSbx)Sr2Ca2Cu3Oy (with x = 0.0, 0.1, 0.2, 0.3, 0.4 and 0.5) have been prepared by the solid state reaction method. Sintering at different temperatures (between 800-8S0 degrees C) and time periods has been carried out in order to study its effect on T-c values. The samples have been characterized by x ray powder diffraction (XRD), Scanning Electron Microscopy (SEM) and measurement of resistance at various temperatures. The study reveals that the incorporation of Sb up to x = 0.2 promotes the formation of a high-T-c 2223 phase and large sintering time helps in reducing the number of unwanted phases. Compositions with x greater than or equal to 0.3 result in the formation of a new monoclinic ''4441 phase'' (along with 2223 and 2212 minor phases) which is non-superconducting down to 77 K. Sintering time at 860 degrees C for samples with x = 0.0, 0.1, 0.2 and 0.3 affects the respective T-c values and the maximum values observed are 94 K, 96 K, 100 K and 87 K, respectively. The samples with x = 0.4 and 0.5 do not superconduct up to 77 K.