Berlin 2012 – wissenschaftliches Programm

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MI: Fachverband Mikrosonden

MI 8: Poster – Microanalysis and microscopy

MI 8.10: Poster

Mittwoch, 28. März 2012, 15:00–17:30, Poster E

Perturbed γ-γ angular correlation – applications in terms of elastic and plastic deformation in MAX phases — •Christoph Brüsewitz¹, Daniel Jürgens¹, Michael Uhrmacher¹, Ulrich Vetter¹, Hans Hofsäss¹, and Michel W. Barsoum² — ¹II. Physikalisches Institut, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, D-37077 Göttingen, Germany — ²Dep. Mat. Sci. & Eng., Drexel University, Philadelphia, PA 19104, USA

The perturbed γ-γ angular correlation (PAC) is used to investigate the neighbourhood of a probe atom at a scale of a few Ångström. The method utilizes the oscillating anisotropy of the depopulated intermediate state in the decay cascade of e. g. implanted ¹¹¹In. This state is split due to hyperfine interactions, originated by the local probe environment. This hyperfine interaction – here caused by an electric field gradient (EFG) at the Al-site of the MAX phase Ti₄AlN₃ – has been studied as a function of uniaxial load. The strength as well as the distribution of the EFG increase with pressure, which can be attributed to a reduction of the lattice spacing and an increase in dislocation density due to the deformation, respectively. Both aspects will be described theoretically by means of DFT calculations and a model concerning the stress field of dislocations. For a quantitative description of the distribution, one additionally has to take grain boundaries, point defects and inhomogeneous stresses into account. The analogy to high-resolution X-ray diffraction will be discussed as a supplemental issue. This work is supported by the DFG under contract HO 1125/19-1.