THE LOW-TEMPERATURE RESISTANCE AND ITS DENSITY EFFECTS OF BULK NANOSTRUCTURED SILVER

The low-temperature DC resistance and its density effects of nanostruc tured Ag (n-Ag) was investigated at temperatures in the range 4.2-300 K. The results indicated that the resistivity of n-Ag (size about 20 n m) exhibited metallic behaviour in the density range 88-99% similar to that of polycrystalline Ag (p-Ag). However, the absolute magnitude of the resistivity was much higher than that of p-Ag and increased with decreasing density. Tile specimen density not only affected the absolu te value of the resistivity but also influenced the temperature coeffi cient of resistivity(TCR). Experiment illustrated that, with decreasin g density, the TCR decreased monotonically, especially for the TCR at low temperatures (30-60 K). In addition, the position of the maximum T CR of n-Ag was higher than that of p-Ag and shifted further to higher temperatures with decreasing density. The high resistivity of n-Ag can be ascribed both to an extrinsic (macro-porosity) effect and to addit ional grain boundary scattering; whereas the TCR of n-Ag being lower a s well as its decrease with decreasing density could be reasonably att ributed to enhancement of electron scattering at grain boundaries and can be interpreted well in terms of an interfacial reflection, model. The shift of the maximum TCR position to high temperature would be a r eflection of the enhancement of atomic coupling within nano-grains, wh ich will be further enhanced by de-coupling of grain boundaries.