Effect of sintering atmosphere on the weak-link behaviour of YBCO superconductors

Weak-link behaviour of YBa2Cu3Ox (1 2 3) superconductors sintered in differ ent atmospheres are studied by measuring the variation of critical current densities (J(c)) near the superconducting transition temperatures (T-c). Th e weak links are found to change from superconductor-insulator-superconduct or to superconductor-insulator-metal-superconductor and superconductor-meta l-superconductor type of junctions as the sintering atmosphere is varied fr om argon to air and oxygen respectively. The scanning electron microscopy i n conjunction with energy dispersive spectroscopy studies indicate that the composition fluctuation at the grain boundaries is the reason for such var iation. (C) 2001 Elsevier Science B.V. All rights reserved.