Analytical Applications of X-ray Excited Optical Fluorescence Spectra

Abstract

A rapid, quantitative analytical technique for the analysis of rare earth impurities is described.The method, X-ray excited optical fluorescence, uses high-energy X-rays to excite the rare earth impu-rities in appropriate matrices.The excited rare earth impurities fluorescence with simple line emission spectra which can be used for quantitative measurements.The experimental equipment employed is similar to that described by Linares et al. and also Sasaki.In the present study the X-ray source is a Machlett OEG-60 tungsten-target X-ray tube driven by a ARL power supply.A sample chamber is shown in Fig.2.The fluorescent radiation is made monochromatic by a Hitachi Perkin-Elmer Model 139 scanning spectrophotometer equipped with a 1440 lines/mm grating blazed at 2000A, and detected with an photomuitiplier (HAMAMATSU TV Co., Ltd.R106) having S-19 response, and a fused silica-envelope.An amplifier equipped in the spectrophoto-meter and a chart recorder (TOA Electronics Ltd., EPR-2T) complete the system.Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er and Tm have been determined by this method with detection limits ranging from 0.2 ppm to 20 ppm in La2O3.Appreciable amounts of Pr, exceeding 500 ppm in some cases was found in commercial La2O3, which had been used as the raw material for optical glass.Spectrum patterns obtained for each rare earth element in La2O3 are also presented.The detection limits in other oxide systems are surveyed and discussed.