Structural and compositional modifications of fayalite Fe2SiO4 under electron irradiation

Electron irradiation induced phase decomposition in fayalite Fe2SiO4 has been observed in situ in a transmission electron microscope at 300 keV. Structural and chemical changes were monitored by electron diffraction and X-ray energy dispersive spectroscopy (EDS). Fayalite was observed to collapse at a fluence of 4 × 1023 e−/cm2, without significant chemical changes. Further phase decomposition is accompanied by strong mass loss, in particular oxygen, which is found to be fully removed for elevated electron fluences. The residual Si and Fe elements rearranged to form Fe,Si nanoparticles.