Growth mechanism of Ag-foil-based artificially superconducting joints of YBa2Cu3O7 monoliths

Abstract

A new method was developed allowing large superconducting YBa2Cu3O7 (YBCO) monoliths having complex shapes to be obtained. This method consists of joining two or more YBCO monoliths, and it is based on the interfacial melting induced by metallic Ag thin foils inserted between YBCO pellets. Studies of the microstructure and the superconducting properties of the joints obtained by using this technology have shown that a perfect interface can be obtained without agglomerations of non-superconducting phases and with a critical current density as high as that of the original blocks. No evidence of Ag precipitates was detected either at the interface or into the YBCO solid matrix, suggesting a migration of Ag. For a better understanding of the interface growth mechanism, we studied the influence of the cooling rate. The knowledge on the Ag diffusion process has enabled us to propose a model for the growth mechanism of the YBCO/Ag/YBCO interfaces.