Equilibrium segregation to grain boundaries has been studied for many years, but only recently have the techniques to quantify such segregation at high spatial resolution become widely available. These include, for example, the Auger surface analysis of fractured samples, or the study of boundaries edge-on in a field emission gun STEM equipped with energy dispersive X-ray analysis or electron energy loss spectroscopy. The key question, however, is whether these different techniques yield the same results when applied to a specific set of samples, and this paper reviews some of the successes and problems associated with such studies.

For STEM analysis of grain boundary segregation, several instruments now routinely give probe sizes of ∼1nm. Hence line profiles across grain boundaries at this level of resolution are quite feasible. However a larger probe with greater probe current and better X-ray counting statistics is often more useful, especially if sample drift is a potential problem.