DETERMINATION OF TRACE RARE-EARTH IMPURITIES IN HIGH-PURITY RARE-EARTH-OXIDES BY X-RAY-FLUORESCENCE SPECTROMETRY

Methods for the determination of individual rare earth (RE) elements have been developed for fifteen RE oxide matrices, viz. La2O3 to Lu2O3 and Y2O3. In general, for each matrix, two or three neighbouring elements on both sides of the matrix element are determined and the minimum determination limit (MDL) is in the range of 0.002-0.01%. These MDLs are the lowest (in many cases) reported so far by any analytical method. Special efforts were made to use a small amount of sample (as low as 400 mg) for the analysis by the use of double layer pellet technique and elaborate critical thickness studies. In some cases, intensity correction factors have been determined for line overlaps. Practical experiences with 15 RE matrices, most of which are investigated for the first time, are discussed.