X-RAY CONTINUUM DISCRIMINATION TECHNIQUE FOR THE ENERGY-DISPERSIVE ANALYSIS OF FINE PARTICLES

Discrimination criteria are proposed for selecting irregularly shaped and unpolished fine grains for quantitative analyses by energy dispers ive X-ray (EDS) spectroscopy. The basic principle is that the energy d istribution of the continuum or background radiation is a direct indic ation of the orientation of the particle surface at the point of analy sis. Background spectra were collected from pure elements in various g eometric configurations and orientations from which it was observed th at the low-energy (<4 keV) portion of the spectra was most sensitive t o the orientation of the specimen surface, showing a strong increase i n intensity with increasing specimen tilt up to about 40-degrees. A si mple ratio of low-high-energy windows in the background radiation prov ided an adequate indication of the orientation of the particle surface . Combination of this discrimination criterion with the requirement th at the analytical total be 60 wt % or better provided oxide analyses f rom garnet and anorthite particles that were within 7% relative standa rd deviation (RSD) for oxides in the 10-40 wt % range and within 9% RS D for oxides in the 1-10 wt % range.