Effect of silver addition on superconductivity in the Bi_1.6Pb_0.4Sr_1.6Ca₂Cu₃O_10−y system

Abstract

Silver/superconductor composites containing 0 to 80 vol% silver have been prepared and their properties determined. Optimum heat treatment at sintering temperatures (∼ 800° C) under low oxygen pressures produces material with high critical current density and improves physical properties. Magnetic susceptibility measurements have been found to be consistent with resistivity results. In order to retain a single high-T _c phase with increasing silver content, decreased oxygen partial pressures are required. Using the normal-state resistivity of these composites, a percolation threshold at a silver volume fraction of ∼43% was observed, while zero resistivity measurements show that a continuous superconducting network can be obtained with up to ∼80 vol% silver. The critical current density of 21 vol% silver-doped samples was found to be 1520 A cm⁻² at 77.3 K, compared to 260 A cm⁻² for an undoped sample.