Although grain boundaries typically account for only a small fraction of a material, they can have far reaching effects on the overall bulk scale properties. These effects are usually simply linked to the boundary having a different atomic arrangement to the bulk. A necessary first step in understanding the structure-property relationships is therefore a detailed determination of the boundary structure.

One means of obtaining detailed information on the structure of grain boundaries is through correlated Z-contrast imaging and electron energy loss spectroscopy (EELS). The Z-contrast image generates a map of the grain boundary which can be used to position the probe in defined locations for spectroscopy. In the case of oxides, a structural model of the metal atom positions can be determined directly from the image. Furthermore, using a simple bond-valence sum minimization routine, the oxygen atoms can be placed so that the structure contains atoms that have valences consistent with their expected formal valence state.