STUDIES OF LOCAL BONDING AND CHEMISTRY AT INTERNAL INTERFACES USING ELECTRON-ENERGY-LOSS SPECTROSCOPY

Changes in the structure, chemistry and bonding at internal interfaces often have a great influence on the properties of materials. High res olution imaging and Energy Dispersive X-ray Spectroscopy in the Transm ission Electron Microscope have been used extensively to study the str ucture and composition at interfaces. Spatially resolved Electron Ener gy Loss Spectroscopy (EELS) in the Scanning Transmission Electron Micr oscope (STEM) offers a new probe to explore the effect of structure an d chemistry changes on the local bonding at interfaces. This paper rev iews the relationship between EELS and electronic structure and illust rates the insights obtained from this technique with the help of examp les which include : a) The effect of B segregation on grain boundaries in Ni3Al and Ni3Si. b) The effect of Bi segregation on grain boundari es in Cu. c) Bonding changes at two metal-ceramic interfaces :Nb-Al2O3 and Cu- Al2O3.