Sintering characteristics of Y-Ba-Cu oxide-Ag-x superconductors under argon atmosphere

Sintering studies on Y-Ba-Cu oxide (YBCO)-Ag-x (x = 0, 0.6, and 1.0 mol) powder were carried out in argon atmosphere to understand the role of silver addition on the densification behavior of these materials. The increase of sintered densities of the compacts with silver addition in argon atmosphere contradicted our earlier observation on sintering of YBCO-Ag-x powder compacts in air, where the densities decreased for x > 0.6. Thermogravimetric (TG) studies under argon atmosphere indicate a continuous decrease of mass on heating suggesting an enhanced rate of oxygen removal from the YBCO matrix that facilitated the sintering in argon atmosphere. Sintering studies of YBCO-Ag-x powder compacts in argon in conjunction with earlier observations in air has substantiated our claim that high-temperature oxygen desorption by the silver from the YBCO matrix to the sintering atmosphere controls the rate of densification for these superconducting composites. However, the apparent activation energies for sintering, suggest that the sintering process is controlled by yttrium ion diffusion along bulk and grain boundaries.