Application of the electron microprobe to quantitative analysis of ferric-ferrous ratio in silicate glasses, new experimental calibration
Final Report Abstract
As a main result of our project we present two new analytical techniques for the determination of the iron oxidation state in silicate glasses by electron probe micro-analysis (EPMA). Both techniques are further developments of the “flank method” previously utilized for Fe-bearing minerals (e.g. garnets and oxides). This method is based on the changes in both intensity and wavelength of the FeLα and FeLβ X-ray emission lines with iron oxidation state. The flank method utilizes the maximum difference for the FeLα and FeLβ spectra observed at the peak flanks between different standard materials, which quantitatively correlates with the Fe2+ content. The accuracy of the Fe2+/ΣFe determination, which depends on both the Fe2+ content determined with the flank method and on the total Fe content, is estimated to be within ±0.1 for silicate glasses with FeOT >5 wt% and within ±0.3 for silicate glasses with low FeOT ≤5 wt%. The application of the flank method on silicate glasses requires minimization of the EPMA beam damage which can be successfully achieved by (method 1) continuous movement of the sample stage under the electron beam during analysis, e.g. with a speed of 2 µm/s, or by (method 2) utilizing Time-Dependent Intensity (TDI) technique.
Publications
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(2018). High spatial resolution analysis of the Iron oxidation state in silicate glasses using the electron probe. American Mineralogist
Hughes, E. C., Buse, B., Kearns, S. L., Blundy, J. D., Kilgour, G., Mader, H. M., Brooker, R. A., Balzer, R., Botcharnikov, R.E., Di Genova, D., Almeev, R. R. & Riker, J. M.
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(2018). Electron microprobe technique for the determination of iron oxidation state in silicate glasses. American Mineralogist
Zhang, C., Almeev, R. R., Hughes, E. C., Borisov, A. A., Wolff, P. E., Höfer, H. E., Botcharnikov, R. E. & Koepke, J.
