Description
This thesis describes an experimental study of the superconducting properties of Bi1.65Pb0.35Sr2Ca2Cu3O10+δ compounds, in samples that have been ball milled for different durations of time. Bi1.65Pb0.35Sr2Ca2Cu3O10+δ displays superconductivity with a transition temperature Tc ≈ 120 K. The high energy ball milling process produced severe damage to the outer layers of the grains in the powdered samples, although for the shorter milling times, the cores of the grains retained their original composition and structure. Measurements of the temperature dependence of the dc magnetic susceptibility, electrical resistivity, thermoelectric potential and thermal conductivity are consistent with a picture in which, for the shorter milling times, the cores of the grains remained superconducting, in spite of the overall damage impinged to the outer layers, which rendered an electrical resistivity behavior more typical of insulators. The values of the upper critical magnetic field could be estimated from the temperature dependence of the thermoelectric potential in magnetic field, from which the coherence length could be estimated.
