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.
Diffusion profile schematic
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.  
One-dimensional tracer diffusion
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.  

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© H. Föll (Defects - Script)