ESTIMATION OF FERMI ENERGY FROM THERMOELECTRIC-POWER MEASUREMENTS ON A C-SHAPED POLYCRYSTALLINE SAMPLE OF BI1.6PB0.4SR2CA2CU2OY

Two cuts were inserted at 90-degrees to each other into a ring-shaped sample of Bi-Pb-Sr-Ca-Cu-O. The first cut lay parallel to the applied temperature gradient, serving to define a vertical symmetry axis. The second cut lay in the middle of the right wing, perpendicular to the symmetry axis, completely interrupting the passage of supercurrents in this wing. The passage of any normal component of current density was made possible, however, by filling up the cut with pure In metal. The left wing was left as sintered. Thermal voltages resulting from the same temperature gradient acting on both continuous and In-filled halves of the sample were detected as a function of temperature around the superconducting transition at about 109 K. Comparing the difference between the thermopowers of the two halves, we are able to calculate the Fermi energy of our superconducting material. The result is 0.13 +/- 0.02 eV, which is in reasonable agreement with other reported data for 2:2:2:3 compounds. We also find agreement between our values of the superconducting number density, n(s), the energy-gap-to-T(c) ratio, 2-delta/k(B)T(c), and those values reported in the literature.