The reactions between iron and selenium

Project files are comprised of 1 page pdf and presentation recording in mp4 format.In the wake of the recent discovery of high-temperature superconductivity in iron selenide, FeSe, chemists, physicists, and materials scientists from around the globe have tried to develop new FeSe-based materials with higher and higher superconducting critical temperatures. However, none have yet explored the fundamental chemistry of how Fe and Se react. We investigated the interactions between solid Fe and Se in the absence of the diffusion limitations often confronted in solid state chemistry by preparing layered precursors of elemental Fe and Se with layer thicknesses on the order of a few angstroms with a variety of Fe/Se compositions. The initial structures and subsequent reactions were monitored via x-ray diffraction and x-ray fluorescence as the precursors were gently annealed. Structural and compositional analysis of the samples indicates that, unlike other transition metal selenides, the reactions between Fe and Se are not kinetically limited by diffusion processes. Even at temperatures well below standard reaction temperatures, thermodynamic products between Fe and Se appear to dominate the macro-architecture of the precursors. These findings may hold significant consequences for the development of future FeSe-based materials, as the low reaction barriers to form the thermodynamic products may impede efforts to kinetically trap metastable FeSe materials.US Department of Energ