### 3.3.2 Essentials to Chapter 3.3 Experimental Approaches to Diffusion Phenomena

| It's easy in principle: You produce and measure a diffusion profile. |  |
|  | Put whatever is supposed to diffuse on the crystal surface (make sure you cope properly with the "dirt" or oxide on the surface). |
|  | Let it diffuse at a defined T for a defined time t. |
|  | Measure the diffusion profile "somehow". |
|  | Fit to a solution of Fick's law = one data point for D(T). |
|  | Repeat at different temperatures until you gave enough data points for an (Arrhenius) D(T) plot. |
| Use isotopes of the material in question for self-diffusion measurements. |  |
| While the intrinsic point defect serving as diffusion vehicle will do a perfectly random walk, the diffusing atom may not. |  |
|  | There is a correlation coefficient f linking measured and theoretical diffusion coefficients. |
DSD(T) | = | f1V · DSD(Theo)
--- | --- | ---
|  | The correlation coefficient f is = 0 for 1dim. diffusion, around 1/2 - 2/3 for 2dim. diffusion (e.g. in the base plane of hexagonal lattices) and around 2/3 - 3/4 for 3dim. diffusion. |
| There are many other ways to obtain diffusion data, none fool-proof and all money and/or time expensive. |

© H. Föll (Defects - Script)