MULTIELEMENT CHARACTERIZATION OF SILICON-CARBIDE POWDERS BY INSTRUMENTAL NEUTRON-ACTIVATION ANALYSIS AND ICP-ATOMIC EMISSION-SPECTROMETRY

Instrumental neutron activation analysis (INAA) and inductively coupled plasma atomic emission spectrometry (ICP-AES) have been optimized for application to a comprehensive analysis of silicon carbide powders. Via medium- and long-lived indicator radionuclides with half lives between 2.3 h (Dy-165) and 12.4 a (Eu-152), INAA can detect 55 elements. Analytical parameters and experimental modes are given with limits of detection obtained for a silicon carbide powder of typical purity grade. For the performance of ICP-AES, a wet-chemical decomposition procedure was optimized for sample portions of about 1 g using a mixture of high-purity conc. HF, HNO3 and H2SO4 for digestion in autoclaves with a PTFE-liner. For all investigated elements, recoveries greater-than-or-equal-to 98% were obtained. By scanning wavelength profiles, interference-free emission lines were found for 56 elements. By the combined performance of INAA and ICP-AES, 66 elements were assayed in the analysed silicon carbide powder. The limits of detection were below 0.01-mu-g/g for 24 elements, they were between 0.01 and 0.1-mu-g/g for 17 and between 0.1 and 1-mu-g/g for 15 elements. The remaining 10 elements were detectable at levels > 1-mu-g/g. The comparison of results of these two methods as well as of results obtained by other laboratories shows that, for the most common impurities, a satisfactory degree of accuracy could be achieved.