Berlin 2012 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 77: Electronic structure I
O 77.6: Vortrag
Donnerstag, 29. März 2012, 17:15–17:30, MA 043
Spectroscopic Characterisation of Insulating and Superconducting Cement 12CaO·7Al2O3 (C12A7) — •Anna Buling1, John McLeod2, Manfred Neumann1, Ernst Kurmaev3, Hideo Hosono4, and Peter Sushko5 — 1D-Fachbereich Physik, Universität Osnabrück — 2CA-Department of Physics and Engineering Physics,University of Saskatchewan — 3RU-Institute of Metal Physics, Russian Academy of Sciences - Ural Division, Yekaterinburg — 4JP-Materials and Structurs Laboratory, Tokyo Institute of Technology — 5UK-University College London
The nanoporous complex oxide C12A7, which is a wide bandgap insulator, is produced as a main constituent of commercial alumina cement but has great potential for other applications in electronics and catalysis. By introducing oxygen deficiency, conductivity can be realized in the system up to superconductivity with a TC ≈0.14 - 0.4 K. Currently, there are two competing models explaning the existence of conductivity in this compound: One involves the electron hopping along framework lattice sites, the other the electron transfer via a cage conduction band.
Here we present the investigation of insulating and superconducting C12A7 by means of X-ray photoemission, X-ray absorption and X-ray emission spectroscopy measurements completed with DFT calculations to illuminate the relations in the conduction and the valence bands. Our measurments suggest that free electrons in oxygen-deficient C12A7 occupy a narrow band which exists between the main conduction band and the valence bands.