EXAFS STUDIES OF BISMUTH DOPED NANOCRYSTALLINE COPPER

Nanocrystalline materials are single- or multiphase polycrystals with a crystallite size in the range of a few nm (typically 5-20 nm), so that about 30 vol. % of the material consists of grain- or interphase boundaries. Characteristic structural features are a reduced atomic density and random atomic arrangement in the grain boundary component. EXAFS studies on bismuth doped nanocrystalline copper show that bismuth segregates in the grain boundaries exhibiting a low coordination of Cu atoms as neighbours. Bi doping causes structural rearrangements in the grain boundaries, in comparison to grain boundaries in undoped nanocrystalline copper, due to a reduction of the free volume in the grain boundaries.