In many cases, high energy resolution for EELS technique is needed to detect the point defects, grain boundaries and heterointerfaces in materials.
Figure 128 compares the EELS profiles taken from a grain boundary and a grain bulk of perovskite-type CaCu3Ti4O12 (with grain sizes of 100-300 µm). Based on HRTEM imaging, it was suggested that the grain boundary exhibited a step-like morphology and high local stress due to the change of chemistry and/or structure. The grain boundary was Cu rich, which was determined by EDS measurements.
Figure 128. Comparison of the EEL spectra of Ti L2,3-edges and Cu L2,3-edges between grain boundary and bulk of CaCu3Ti4O12. Adapted from 
Table 128. Valence states of Ti and Cu in a grain boundary and a grain bulk of CaCu3Ti4O12.
 C.C. Calvert, W.M. Rainforth, D.C. Sinclair, and A.R. West, EELS analyses at grain boundaries in CaCu3Ti4O12, Journal of Physics Conference Series 02/2006; 26(1):65.