Six different compositions in ( Bi 1.5 Pb 0.5−x Sb x) Sr 2 Ca 2 Cu 3 O y (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 800–860° 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 ≥ 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°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.

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The effect of a small amount of Sb doping (5%) on the formation of the high temperature superconducting phase has been investigated on the Bi 1.5 Pb 0.5 Sr 2 Ca 2 Cu 3 Oy compound. It is observed that at 860 • C the Tc zero (T 0 c ) value depends on the sintering time. It first increases to a maximum value of 96 K and then decreases to a stable lowest value of 88 K. The samples have been characterized by X-ray diffraction (XRD), four probe electrical resistance and current density measurements. The XRD revealed the presence of two phases: an orthorhombic high-Tc 2223 phases with lattice constants a = 5.395Å, b = 5.508Å, c = 37.0422Å and another tetragonal low-Tc 2212 phase with lattice constants a = b = 5.419Å, c = 30.832Å.

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