Abstract
Au, Pd and Au-Pd alloys, electrodeposited, respectively, from neutral chelate cyanide bath, ammonium phosphate complex bath and mixed bath of them were studied by utilizing T. E. M. and S. E. M. and also by measuring microhardness. Electron diffraction analysis revealed that the electrodeposited Au-Pd alloy formed a solid solution since, at the early stage of nucleation, solid solutions were formed over all alloy constituents. The lattice parameter of the alloys changed nearly according to Vegard's law. The nucleation density for alloy deposition was about 3×1011cm-2, and was nearly equal to that for Au or Pd deposition. Film growth by electrodeposition was of the following process; nucleation→island crystal→network crystal→plate crystal. Electrodeposits showed no orientation in the initial stage of nucleation, but growing to island or network crystal they gradually took an epitaxy with Cu substrate. The alloy films contained finer crystallites and more microtwines than that of individual Au or Pd. This effect is considered to relate with the increase of lattice strain caused by alloying. Alloy films of less than 50 at. % Pd showed smooth and fine surfaces, but those containing more Pd precipitated powdery, grayish-black and no adherent crystallites on their surfaces. Hardness of the alloy films increased with an increase in Pd content.
