The Mössbauer Effect: A New Method for Measuring Diffusion
We have been able to directly observe atomic diffusion in solids by observing the broadening of the Mössbauer line. There appears to be some advantage to the technique over the more common tracer-sectioning technique for measuring diffusion. In addition to the fact that the technique does not require the destruction of the sample, thereby permitting the measurement of the temperature dependence of the diffusivity with a single specimen, it may afford more accurate results for very rapidly diffusing ions. It also may give a direct handle on the Bardeen-Herring correlation factor, particularly in the cases where the diffusing ion undergoes a very highly correlated motion through the lattice, as is expected for vacancy diffusion of impurities, where the binding energy between the impurity and the vacancy is very large. Our data indicate that the temperature dependence of the broadening of the Mössbauer line follows an Arrhenius relation, with a slope parallel to the classical diffusivity for cases which are not highly correlated. In the cases so far studied the broadening is only half of the earlier theoretically predicted value, and the significance of this point is discussed. A novel furnace assembly used for hot-source and hot-absorber experiments under 1100°C is given.
KeywordsBoron Nitride Measuring Diffusion Mossbauer Spectrum Vacancy Mechanism Iron Diffusion
Unable to display preview. Download preview PDF.