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Fig. 2: X-ray appearance near-edge structure (XANES) (left axis) and XMCD signal (right axis) at the Os L2 and L3 edges in Sr2CrOsO6. The inset shows the element-resolved magnetic moments of Cr (µCr) and Os (µOs), the total magnetic moment (µtot), and the lattice distortion as determined from neutron scattering data refinement [1]. Fig. 1: Rietveld refinements of the neutron powder data of Sr2CrOsO6 taken at 553 K. The observed and calculated diffraction intensities as well as the difference pattern are shown. The upper left inset shows a view along the [111) direction revealing the rhombohedral structure of the double perovskite. The upper right inset shows the temperature dependence of the Sr2CrOsO6 (444) diffraction peak (cubic) splitting into a (404) and (0 0 12) peak (hexagonal). The XMCD measurements on the Os L2,3 edges were performed at the European Synchrotron Radiation Facility (ESRF) at beamline ID12. As shown in Fig. 2 a very clear XMCD signal is observed, signaling a strong local magnetic moment at the Os site opposite to the net magnetization. The experimentally determined value is in good agreement with the neutron scattering result. We have unambiguously demonstrated that an increase of the number of 5d electrons leads to an increase of the transition temperature in ferrimagnetic double perovskites irrespective of the changes in conductivity. Fully spin-polarized conductivity, as indicated by the large induced magnetic moments and supported further by band-structure calculations, can be changed from half-metallic behaviour (known in Sr2CrWO6 and Sr2CrReO6) to insulating behaviour in the high-Curie-temperature ferrimagnetic insulator Sr2CrOsO6. In collaboration with MPI Stuttgart (K. Mogare, M. Jansen, M. Reehuis), KTH Stockholm (A. Delin, G. Vaitheeswaran), and ESRF Grenoble (F. Wilhelm, A. Rogalev). Support by DFG (AL 560/4). [1] Y. Krockenberger, K. Mogare, M. Reehuis, M. Tovar, M. Jansen, G. Vaitheeswaran, V. Kanchana, F. Bultmark, A. Delin, F. Wilhelm, A. Rogalev, A. Winkler, and L. Alff, Phys. Rev B 75, 020404(R) (2007). - 80 -
SiCN/C-Ceramic Composite as Anode <strong>Material</strong> for Lithium Ion Batteries Robert Kolb, Claudia Fasel, Verena Liebau-Kunzmann, Ralf Riedel The choice of electrode and electrolyte materials to design lithium batteries is limited due to the chemical reactivity of the used materials during the intercalation/deintercalation process. Amorphous silicon carbonitride ceramics (SiCN) are known to be chemically stable in corrosive environments and exhibit disordered carbonaceous regions making it potentially suitable to protect graphite from exfoliation. The material studied in this work was synthesized by mixing commercial graphite powder with the crosslinked polysilazane VL20 ® . Pyrolysis of the polymer/graphite compo<strong>und</strong> at appropriate temperatures in inert argon atmosphere resulted in the formation of an amorphous SiCN/graphite composite material. First electrochemical investigations of pure SiCN and of the SiCN/C composite are presented here. A reversible capacity of 474 mAhg -1 was achieved with a sample containing 25 wt% VL20® and 75 wt% graphite. The measured capacity exceeds that of the used graphite powder by a factor of 1.3 without any fading over 50 cycles. Potential [V] vs. Li/Li + 3,5 3,0 2,5 2,0 1,5 1,0 0,5 0,0 450°C 650°C 850°C 1050°C 1250°C Graphite 0 100 200 300 400 500 600 700 Capacity [mAhg -1 ] Fig. 1: First charge- and discharge of 25VL20-75C samples pyrolysed at different temperatures compared to pure graphite vs. Li/Li + . - 81 -
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ANNUAL REPORT 2 0 0 6 FACULTY OF MA
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Annual Report 2006 Faculty 11 Mater
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Preface The year 2006 of the Depart
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difference of numerical and analyti
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Institute of Materials Science Phys
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Research Projects Bulk Amorphous Al
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el Dsoki, C.; Landersheim, V. ; Kau
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Das, J.; Kim, K. B.; Xu, W.; Wei, B
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Staff Members Head Prof. Dr. Jürge
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Zhou L.; Rixecker G.; Aldinger F.;
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concerned with the synthesis and ch
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Publications Fleissner, A.; Schmid,
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• Surface analysis The UHV-surfac
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T. Mayer, U. Weiler, E. Mankel and
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Thin films The Thin Film division w
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Gregori, G.; Kleebe H.-J.; Sorarù,
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Hessische Industriemüll GmbH). Due
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Technical Personnel Josef Kolb, Dip
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Research Projects Environmental sca
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Fig. 1: Aerial photo of the Lake Li
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Lithological Map of the Japanese Ar
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tower stripping, and therefore much
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Diffusion and reaction in micro- an
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Rift dynamics, uplift and climate c
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Geology, land use change and erosio
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nearly half a century has been perf
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The Effect of LiF Addition on the S
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In case of the undoped sintered B6O
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Microstructures in Omphacite and Ot
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Modelling phase-assemblage diagrams
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As an example, Fig. 2 shows the che
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MATERIALS SCIENCE Physical Metallur
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