Thermoelectric power studies on the BPSCCO system with silver addition

Abstract

The effect of silver addition on the superconducting properties (resistance and thermoelectric power) of the Bi_1.6Pb_0.4Sr_1.6Ca₂Cu₃O_y superconductor 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 through the grain boundaries of the rather low-density, 2223 material weakening the intergrain coupling. T_c0 (zero resistivity transition) is thus reduced with the addition of silver. The normal state thermoelectric power (TEP) of these specimens has been fitted to a formula derived from marginal Fermi liquid hypothesis. The normal state value of TEP decreases with increasing silver concentration. T_s0(zero TEP temperature) is almost the same for all these specimens and is higher than T_c0, confirming a lower percolation threshold for TEP than the percolation threshold for conductance.