Coupled SEM-EDS-RAMAN: A complimentary approach for characterisation – Application to geomaterials

Abstract A combination of morphological, chemical, and crystallographic analysis is frequently required to characterise materials. Spectroscopic and/or imaging techniques are required to access a thorough knowledge of the sample, to better understand the structural, chemical, and textural factors that control their properties, their behaviour, and their reactivity, … Among these techniques, scanning electron microscopy and micro-Raman (μ-Raman) spectroscopy occupy a major place and have often been combined. The scanning electron microscope (SEM) provides information on morphology, topography, and chemistry, supplemented by electron beam-based techniques providing chemical or crystallographic information (EDS, WDS, EBSD, cathodoluminescence, etc.). μ-Raman is also widely used in materials characterisation. In geoscience, Raman offers information that includes, among others, polymorphism, crystallography, temperature and stress effects, complementary to that obtained from SEM. Both are often used in parallel. Switching from one to the other is in some cases considered a problem that cannot be solved easily. Then, coupling SEM-EDS and Raman on a unique system is an efficient method for the physicochemical characterisation at the micro/nanometric scale. The technical aspects of coupling are described, as well as practical aspects and limitations inherent in this coupling. The interest will be illustrated by application examples, including cultural heritage, and naturally occurring asbestos (NOA).