Electron energy-loss spectroscopy and the crystal chemistry of rhodizite. Part 2.—Near-edge structure

Abstract

An electron microscope fitted with a magnetic prism spectrometer and a parallel recording system has been used to measure the electron energy-loss spectrum of the mineral rhodizite at an energy resolution of 0.5 eV. The near-edge structures associated with the oxygen and aluminium edges have been analysed using both well established and novel techniques. We are able to confirm the presence of aluminium in octahedral sites and to determine the relative site occupancies of the oxygen in three chemically inequivalent sites. These occupancies are in agreement with those derived from X-ray diffraction, high-resolution electron microscopy and nuclear magnetic resonance data. Measured chemical shifts are consistent with the predictions of a simple charge potential model. X-ray photoemission and Auger spectra were also measured, and the conclusions drawn from them are in agreement with our interpretation of the structure of the oxygen K-edge based on the electron energy-loss spectra.