Interesting and unexpected long Ag and Cu whiskers are found in Ag-Cu-Te alloys annealed at 400℃ and 600℃. Depending upon the nominal compositions of the alloys, there are three kinds of whiskers, Ag, Cu, and Ag+Cu whiskers. For the first time, two different kinds of whiskers grown simultaneously from the same substrate are observed. These whiskers are all polycrystalline, and the grain sizes of the Ag are larger than those of Cu. The formation mechanisms of these whiskers are analyzed and are associated with stress resulting from the two regions of significantly different compositions in the solidified samples, as well as the liquid-like structures of these alloys.
In the study of liquidus projections of the Ag-Cu-Te and Ag-Cu-Se ternary systems, interesting spherical-shaped microstructures are observed in some of the solidified alloys. In the as-cast microstructures of inorganic materials, dendritic phases, which indicate primary solidification phases, are the most easily distinguishable microstructures. The much less common spherical-shaped microstructures suggest that these alloys passed through two-liquid phase regions, known as liquid-miscibility gaps, during their solidification paths.
The interfacial reactions in Co/GeTe couples were examined. The couples were prepared by electroplating Co onto a GeTe substrate. After reacting at 500 °C for 14 days, β-CoTe, β-Co₅Ge₃, and CoGeTe phases formed at the Co/GeTe interface. Unexpected reactions involving all three phases were observed on the outer side of the Co layer, which was not in direct contact with the GeTe substrate. A solid-gas reaction at 500 °C was conducted to verify the source of the reactants, yielding results similar to those observed in the Co/GeTe couples. The Co-Ge-Te phase diagrams and predominance area diagrams were calculated to provide a better understanding of these unexpected reaction results.