ANALYSIS OF RARE EARTH MATERIALS BY CATHODOLUMINESCENCE SPECTRA EXCITED IN AN ELECTRON MICROPROBE

The optical fluorescence (cathodoluminescence) emitted by some materials when they are irradiated by a sharply focused beam of electrons provides an exceptionally powerful means of detecting and determining impurities at very low absolute concentration levels. The focused beam provided by electron microprobe instruments is ideally suited for these applications, because the beam size may be reduced to areas less than 1 µ2 Thus, spectroscopic analysis of the emitted radiation can provide information on the spatial distribution of impurities as well as the overall composition of the sample. Detection limits as low as 50 ppb have been obtained for rare earth elements in ideal host materials such as La203 and Y203. Considering the volume sampled by the electron beam, this corresponds to an absolute detection limit of 10-16 gram, a level seldom obtained by other analytical techniques. Several problems involved in quantitative analysis are conside ed and methods for circumventing these are discussed. © 1969, American Chemical Society. All rights reserved.