Anomalous thermoelectric power of Ag-containing (Bi,Pb)4Sr3Ca3Cu4Ox-type superconductors prepared by a glass-ceramic method.

Abstract

Accurately measured electrical resistivity and thermoelectric power of (1--10 wt. %)-Ag-containing (Bi,Pb${)}_{4}$${\mathrm{Sr}}_{3}$${\mathrm{Ca}}_{3}$${\mathrm{Cu}}_{4}$${\mathrm{O}}_{\mathit{x}}$-type superconductors prepared by a glass-ceramic method are reported. Due to the presence of Ag, the volume fraction of the superconducting 2223 phase is found to be highly reduced. Though the variation of resistivity with temperature shows normal behavior, the temperature variation of thermoelectric power (or Seebeck coefficient S) of the Ag-containing glass-ceramic superconductor is highly nonlinear showing both positive and negative values consistently for all the compositions studied. Unlike many other oxide superconductors, the two-band model of Xin et al. [Phys. Rev. B 48, 557 (1993)] is not adequate to explain the said anomalous thermoelectric power data of the present system. The appearance of double peaks in the S versus temperature curves of the samples support the phonon drag effect. \textcopyright{} 1996 The American Physical Society.