• Chumak, I.
• Knapp, Michael
• Ehrenberg, H.

Abstract

samples with varying B contents. This BO3 group connects the octahedral chains perpendicular to the c-axis (Fig. 1). The indices of distortion indicate that the incorporation of boron leads to more regular polyhedra and a rotation of the AlO6 octahedra. Nevertheless, distance least squares refinements (DLS) were necessary to determine the local BO3 configuration. The DLS calculations yielded split positions for the oxygen atoms directly linked to B leading to a local distortion of the octahedral geometry verified in the crystal-structure refinements. This crystallographic model including the split positions for the oxygen atoms of the AlO6 octahedron provides an explanation for the anisotropic behavior of the lattice parameters upon B-incorporation. pressures of about 14-23 GPa in static experiments [1-3]. Shock wave experiments have been performed with subsequently sample recovery to investigate the high-pressure phase [4]. References: 3. Schneider, H., et al. (2008) J Eur Ceram Soc, 28(2), 329-344. 4. Griesser, K.J., et al. (2008) Mineralogy and Petrology, 92(3-4), 309-320. 6. Zhang, G.M., et al. (2010) J Eur Ceram Soc, 30(12), 2435-2441. The Rietveld-refinement of the lattice constant of rs-AlN gives a value of a = 4,044Å, which is in good agreement with the HRTEM results. The crystallite size of the starting w-AlN and the synthesised rs-AlN was determined with XRD and TEM. We come to the conclusion, that the phase transition has a crystallite size The powders were characterised with X-ray diffraction and Rietveld full-pattern fitting. However, no pure rs-AlN phase was produced, but a phase mixture of w-AlN, rs-AlN and different AlO-N phase. The oxygen-bearing phases, esp -AlON with spinel structure and the 27R polytypoid of Al(O)N, gives a rough estimation of the shock temperature. We observe a sluggish phase transition caused by the kinetic barrier and a temperature-activated re-conversion. A vibration band in the IR-spectrum at about 490 cm-1 is assigned to the rs-AlN. Furthermore, solid state 27Al-NMR studies were conducted, showing a chemical shift of 2 ppm for the sixfold Al-N coordination. References [1]I. Gorczyca, N.E. Christensen, P. Perlin, P. I. Grzegory, J. Jun, M. Bockowski, Solid State Commun. 1991, 79, 1033. [2] M. Ueno, A. Onodera, O. Shimomura, K. Takemura, Phys. Rev. B 1992, 45, 10123. [3] Q. Xia, H. Xia, A.L. Ruoff, J. Appl. Phys. 1993, 73, 8198. High Pressure Res. 2012, 32, 23. MS20-T06 Karlsruhe Institute of Technology, Institute for Applied Materials - Energy 2 Karlsruhe Institute of Technology, Institute of Inorganic Chemistry, 1 Fig. 1: crystal structure of B-mullite. Oxygen vacancies are indicated by squares. Only one out of many possible distributions [7] of oxygen vacancies, T3O groups and BO3 groups is shown. Two new binary Li-In phases are detected during galvanostatic Liextraction from the alloy Li13In3 (Li4.33In). The crystal structures of new compounds were determined by single-crystal X-ray diffraction. The compositions obtained after structure refinements were: Li9.95In5.05 (trigonal crystal system, Pearson symbol hP15 , space group P-3m1 (No. 164), a = 4.7480(7) Å, c = 14.283(3) Å) and Li8.37In3.63 (hexagonal, hP12, P6/mmm (No. 191), a = 4.6975(7) Å, c = 11.526(2) Å). The structure of Li 9.95In5.05 can be described as derivative from the CdI2 typ. Li8.37In3.63 can by derived from the Li2Pt structure. MS20-T05 Structural Characterisation of shocked AlN-powders 1 TU Mi

Topics

• impedance spectroscopy
• compound
• phase
• x-ray diffraction
• experiment
• Oxygen
• anisotropic
• phase transition
• transmission electron microscopy
• Boron
• Nuclear Magnetic Resonance spectroscopy
• space group
• dynamic light scattering
• mullite