Quantitative X-Ray Microanalysis

Abstract

With the EPMA and the SEM one can obtain quantitative analyses of ~1-µ³ regions of bulk samples using a nondestructive x-ray technique. For samples in the form of thin foils and sections of organic material, the size of the analyzed microvolume is reduced to about one tenth of the value for bulk samples. For metals and alloys the ZAF technique is usually employed. Pure element or alloy standards can be used and the surfaces of the samples and standards must be properly prepared and analyzed under identical operating conditions. For geological samples the a factor or empirical technique is usually employed. For this class of samples secondary x-ray fluorescence is usually not significant and oxide standards of similar atomic number as the sample are used. Biological samples are often adversely affected by the impinging electron beam. It is important to ensure that the standards are in the same form and matrix as the specimen. The purpose of this chapter is to describe in some detail the various methods by which quantitative analyses can be obtained for inorganic, metallic, and biological samples in the form of bulk specimens, small particles, thin films, sections, and fractured surfaces.