Regensburg 2022 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 21: Transport in Materials: Thermal transport
MM 21.9: Vortrag
Mittwoch, 7. September 2022, 12:30–12:45, H45
Investigation of Phase Transitions in Polycrystalline Tungsten Trioxide Films during Ion Insertion and Extraction by in Situ Transmission and Raman Spectroscopy — Markus S. Friedrich1,2, Alexander G. Strack1,2, Paul K. Tuchecker1,2, •Jan L. Dornseifer1,2, and Peter J. Klar1,2 — 1Institute of Experimental Physics I, Giessen, Germany — 2Center for Materials Research, Giessen, Germany
The International Energy Agency stated in its "European Union 2020 Energy Policy Review" that in 2016 in the European Union alone 152 TWh where consumed for air conditioning (AC), despite only six percent of the global stock of AC units is operated in the EU. So called "smart windows", e.g. windows based on electrochromic materials, such as tungsten trioxide, are promising candidates to reduce this kind of energy consumption. The coloration and bleaching of the EC material is based on the reversible insertion and extraction of small ions inside the material. Ion diffusion plays a key role in this process and therefore needs to be understood in depth in order to enable the optimization of future devices. Burkhardt et al. found, that the diffusion coefficient in this material is dependent on the concentration of already incorporated ions. We suggest, that this originates from changes in the crystal structure of the thin films. To substantiate this suggestion spatially and temporally resolved in situ transmission and Raman spectroscopic experiments were performed during potentiostatic ion insertion and extraction to correlate the diffusion of small ions inside the material with changes of its crystal structure.