THERMOELECTRIC-POWER STUDIES ON THE BPSCCO SYSTEM WITH SILVER ADDITION

The effect of silver addition on the superconducting properties (resis tance and thermoelectric power) of the Bi1.6Pb0.4Sr1.6Ca2Cu3Oy superco nductor has been studied for silver concentrations of 0, 5, 10, 20 and 50 wt.%. Silver is found to be nonreactive in so far as the onset T(c ) is found to remain unchanged at 110 K. Silver, however, diffuses thr ough the grain boundaries of the rather low-density, 2223 material wea kening the intergrain coupling. T(c0)(zero resistivity transition) is thus reduced with the addition of silver. The normal state thermoelect ric power (TEP) of these specimens has been fitted to a formula derive d from marginal Fermi liquid hypothesis. The normal state value of TEP decreases with increasing silver concentration. T(s0)(zero TEP temper ature) is almost the same for all these specimens and is higher than T (c0), confirming a lower percolation threshold for TEP than the percol ation threshold for conductance.