Electron microscopy and associated with it analytical techniques (e.g. EDS, WDS, EBSD etc.) are very important investigation tools in metallography. The advantage of the method is in combinatory structural and analytical approach to sample characterisation with high spatial resolution. In addition to already existing techniques JEOL recently developed a new type of wavelength dispersive spectrometer (WDS) that can be mounted on common scanning electron microscopes (SEM) or electron microprobes (EPMA). This new state-of-the-art Soft X-ray Emission Spectrometer (SXES, Fig. 1) exhibits excellent spectral resolution (0.3eV at Al Ll) and sensitivity. It utilizes a varied-line spaced diffraction grating, allowing the efficient and parallel collection of very low-energy X-rays (so called “soft” X-rays). Two models of the spectrometer are covering wide energy ranges: from 50 eV to 210 eV (SXES-LR) and from 100 keV to 2300 keV (SXES-ER). High spectral resolution allows for analysis of chemical state of an element and spectral differences due to anisotropic bonding.

Here we present some examples of metallographic applications of the new spectrometer. SXES-ER provides new possibilities for chemical mapping of transition metals in various chemical states (e.g. metal, oxide etc.). The chemical state of transition metals such as Fe, Mn and Cr can be evaluated using L emission lines. Effects of self- absorption measured at various voltages can be used to monitor oxidation state of an element [1]. The advantage of SXES-ER for such examination is in parallel detection, similar to EDS, thus flexibility in determination of ROIs for mapping as well as high sensitivity (low noise) of the detector. The spectrometer was also used to map distribution of Li in Cu-Al based alloys, which is important application for the airspace industry [2]. Fine structure of CKa(2) emission peak measured with SXES-LR was used to characterise DLC coatings containing various metals [3, 4]. More information on SXES spectra of wide range of materials can be found in the Handbook of SXES [5].


References
[1] T. Yokoyama et al., Microscopy, 2022, accepted for publication.
[2] C. MacRae et al., Microscopy and Microanalysis, 2018, 24(4), 325-341
[3] W. Tillmann et al., Applied Surface Science Advances, 2021, 5, 1-8.
[4] W. Tillmann et al., Materials Letters, 2021, 284, 1-4.
[5] M. Terauchi et al., Handbook of Soft X-ray Emission Spectra, Version 7, 2021