Glass-Transition-Like Behavior of Grain Boundaries in Nanocrystalline Gold

Characteristic property changes were observed for high density and high purity nanocrystalline (n-) Au prepared by the gas deposition method. The increase in internal friction with a modulus defect started at 180 K and became steep above 200 K. An increase in endothermic heat flow began at 170 K. The electrical resistivity showed a deviation from a linear increase with the temperature at 130 K. All the characteristic changes were reproduced by the repetition of the thermal cycle below 300 K, but the amounts diminished after the grain growth. These characteristic temperature changes indicate a glass-transition-like behavior of the grain boundaries in n-Au.