Sample-substrate interactions during melting of Bi-2212 on Ag

During melt-processing of Bi2.2Sr2.05Ca0.95Cu2Ox (Bi-2212) thick films and bulk components, a liquid phase is formed which dissolves silver from the silver substrate. The dissolved silver precipitates during cooling as soon as the Bi-2212 phase is reformed. The amount of silver taken up from the substrate during the whole heat treatment is 3 wt% if the maximum processing temperature Tmax does not exceed 910 deg. C and 4 wt% if Tmax > 910 deg. C if the starting Bi-2212 powder contained no silver. If 2.7 wt% silver were added to the raw Bi-2212 powder the final silver amount of fully processed samples is 3.5 wt% if Tmax < 910 deg. C, but still 4 wt% if Tmax > 910 deg. C. Excessive grain boundary corrosion of the silver substrate can be avoided by adding 2.7 wt% silver to the raw Bi-2212 powder prior to processing. (author)