Conductivity and superconductivity of (Bi,Pb)-Sr-Ca-Cu-O

The (Bi,Pb)-Sr-Ca-Cu-O glass-ceramics may be considered as disordered metal and superconductor. Depending on the heat treatment conditions the materials are either composed of the oval grains of the 2212 or 2201 phases embedded in the insulating matrix or they mainly contain the 2212 plate-like crystallites weakly connected one with another. The materials have large resistivity and usually large negative temperature coefficient of resistivity (TCR). The granular and disordered character of the materials is also reflected in their superconducting properties. Both the normal-state and superconducting properties correlate one with another. The glass-ceramic samples were obtained by annealing the amorphous solid at temperatures between 840 and 860 degrees C. The measurements of the temperature dependence of resistivity in annealed samples were carried out with the conventional four-terminal method in a temperature range from 3 to 300 K. (c) 2007 Elsevier B.V. All rights reserved.