Influence of crystal orientation on oxygen analysis in NiO with energy dispersive X-ray analysis

Characteristic X-ray spectra of stoichiometric NiO were investigated by EDX. Peak intensities of Ni-Kalpha and O-Kalpha are determined for several zone axes and also off-axis specimen orientations. The intensity ratios depend strongly on specimen orientation, resulting in errors of up to 30% in concentration analysis. Based on Bloch wave calculations, the dependence on the zone axis is explained qualitatively by the ordered structure of NiO, assuming the atoms to be ideal point scatterers. However, in order to get a quantitative description this simple model is not sufficient: the spatial structure of the electron shells must also be considered.