MICROSTRUCTURAL ANALYSIS OF INTERFACE BETWEEN YBA2CU3O7-X AND AG PD ALLOYS/

Pure silver and palladium/silver alloy in a 10/90 weight ratio were ei ther sandwich-coupled or powder-mixed with YBa2Cu3O7-x (Y123) to prepa re Ag-Y123 and (Pd/Ag)-Y123 composites. The reaction and diffusion of elements near the interface of Ag-Y123 or (Pd/Ag)-Y123 were determined by means of differential thermogravimetry (DTA), optical microscopy ( OM), scanning electron microscopy (SEM), transmission electron microsc opy (TEM), energy-dispersive X-ray spectroscopy (EDS), and precision X -ray diffraction (XRD) analyses. The results reveal that the Pd, Ag, a nd Cu react to some extent: Cu will diffuse into pure Ag or Pd/Ag allo y. Conversely, Pd and Ag in pure Ag or Pd/Ag will diffuse toward Y123 at temperatures greater than 945-degrees-C. Diffusion of Cu into pure Ag or Pd/Ag alloy will decrease the melting point of the Ag or Pd/Ag a lloy due to formation of a solid solution and/or an eutectic constitut ion. Since molten Cu/Ag or Cu/Pd/Ag alloys can flow across the interfa ce by means of capillary force between Y123 grains, they fill up the v oids (or capillaries) between Y123 grains and Ag or Pd diffuse into Y1 23 grains, occupying Cu sites in Y123. This is consistent with the res ults of precision XRD, which show the expansion of the Y123 lattice ca used by the occupation.