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Role of segregating impurities in grain-boundary diffusion
1Department of Materials Science and Engineering, Lehigh University, Bethlehem, Pennsylvania 18015, USA.
The Journal of Chemical Physics
|March 17, 2007
Summary
Impurity segregation significantly slows grain-boundary diffusion by blocking sites, as shown by kinetic Monte Carlo simulations. This finding helps explain diffusion in doped ceramic oxides.
Area of Science:
- Materials Science
- Physical Chemistry
- Computational Materials Science
Background:
- Grain-boundary diffusion is crucial for material properties and performance.
- Impurity segregation at grain boundaries can significantly alter diffusion kinetics.
- Understanding this impact is key for designing advanced materials, particularly ceramic oxides.
Purpose of the Study:
- To investigate the effect of impurity segregation on grain-boundary diffusion.
- To quantify the relationship between impurity concentration and grain-boundary diffusivity.
- To interpret simulation results using site-blocking models and relate them to experimental data.
Main Methods:
- Kinetic Monte Carlo (KMC) simulations were employed to model boundary transport.
- Simulations considered both slab and pipe geometries for grain boundaries.
- An analog of the experimental sectioning method was used to determine diffusivity as a function of impurity concentration.
Main Results:
- Impurity segregation was found to retard grain-boundary diffusion.
- The degree of diffusion retardation correlated with impurity concentration.
- Site-blocking models, considering local free volume, explained the observed diffusion retardation.
Conclusions:
- Impurity segregation acts as a significant barrier to grain-boundary diffusion.
- The KMC simulation approach provides a valuable tool for understanding diffusion mechanisms in materials.
- Results offer insights applicable to experimental studies of grain-boundary diffusivity in doped ceramic oxides.
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