Conductivity and Superconductivity of (Bi,Pb)$\text{}_{4}$Sr$\text{}_{3}$Ca$\text{}_{3}$Cu$\text{}_{4}$O$\text{}_{x}$ Glass-Ceramics

In the (Bi,Pb)-Sr-Ca-Cu-O system, materials of various electrical and superconducting properties may be produced by a glass-ceramic method. Phase composition, structure, microstructure and also electrical properties of the material change as a result of heat treatment. Depending on the heat treatment conditions, either a superconductor with the critical temperature between 8 and 105 K or material without a superconducting transition may be obtained. The properties of the material change so much because during annealing three oxide superconductors belonging to the bismuth family are formed. (Bi$\text{}_{0.8}$Pb$\text{}_{0.2}$)$\text{}_{4}$Sr$\text{}_{3}$Ca$\text{}_{3}$Cu$\text{}_{4}$O$\text{}_{x}$ glass was prepared by a standard technique of quenching homogenized and melted substrates. The glass-ceramic samples were obtained by annealing of the glass beneath melting temperature. Structure and microstructure of glass-ceramic samples were studied with scanning electron microscopy and X-ray diffraction method. Superconducting properties were studied by means of electrical conductivity and magnetization measurements. In this paper we present the influence of the phase composition, structure and microstructure on the electrical conductivity in the normal state and the superconducting properties of (Bi,Pb)$\text{}_{4}$Sr$\text{}_{3}$Ca$\text{}_{3}$Cu$\text{}_{4}$O$\text{}_{x}$ glass-ceramics.