Papers by Keyword: Vacancy Diffusion Mechanism

Abstract: Nuclear relaxation caused by diffusion of ¹¹¹In/Cd probe atoms was measured in four phases having the tetragonal FeGa₃ structure (tP16) using perturbed angular correlation spectroscopy (PAC) and used to gain insight into diffusion processes in phases having more than one diffusion sublattice. The three indide phases studied in this work have two inequivalent and interpenetrating In-sublattices, labeled In1 and In2, and nuclear quadrupole interactions were resolved for probes on each sublattice. The phases are line-compounds with narrow field-widths. Diffusional relaxations, fitted using an exponential damping ansatz, were measured at the two opposing boundary compositions as a function of temperature. “High” and “low” relaxation regimes were observed that are attributed to In-poorer and In-richer compositions, under the reasonable assumption that the atomic motion occurs via an indium-vacancy diffusion mechanism. Relaxation was observed to be greater for tracer atoms starting on In2 sites in the indides immediately following decay of ¹¹¹In into ¹¹¹Cd, which is attributed to a preference of daughter Cd-tracer atoms and/or indium vacancies to occupy In1 sites. Activation enthalpies for relaxation are compared with enthalpies for self-diffusion in indium metal.

Abstract: The importance and generality of Kirkendall discovery, which opened new area in diffusion science, have been discussed. The developments of Kirkendall’s idea for sub-surface (SS) and grain boundary (GB) interdiffusion have been considered and applied for the advanced structural materials, such as thin films and nano-composites. The kinetics and mechanisms of SS and GB Kirkendall effects have been analyzed theoretically and studied experimentally.