Impurity states in grain boundaries and adjacent crystalline regions. I. Temperature dependence of the population of states in the grain-boundary diffusion zone.

Abstract

We present the results of an investigation by emission nuclear \ensuremath{\gamma}-resonance spectroscopy of the population of states in the grain-boundary diffusion (GBD) zone. It is shown that atomic probes in polycrystals of some fcc and bcc metals only populate two discrete states in the GBD zone: one in the core of the grain boundary and one in the lattice sites adjacent to the grain boundary. For the typical fcc metals Pd, Pt, and Au, we investigated the dependence of the impurity-state populations on the temperature of the atomic-probe diffusion. It was shown that the ``intrinsic'' temperature dependence of state populations can be distorted owing to the formation of interstitial impurity segregation. In gold, where the volume solubility of such impurities is low, there is a temperature range of diffusion annealings, where the population-state regularities are determined by the ``intrinsic'' parameters of the atomic-probe diffusion. We made a suggestion concerning the atomic-probe diffusion mechanism in the interstitial impurity segregation zone, which causes the atomic-probe ``pumping'' parameters to change at low temperatures.