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KR: Fachgruppe Kristallographie

KR 8: Poster Crystallography

KR 8.3: Poster

Mittwoch, 2. April 2014, 17:00–19:30, P4

Crystallografic orientation of hydrogen defects in lithium niobate and lithium tantalate — •Thomas Köhler, Erik Mehner, Juliane Hanzig, Günter Gärtner, Hartmut Stöcker, and Dirk C. Meyer — Institut für Experimentelle Physik, Technische Universität Bergakademie Freiberg, D-09596 Freiberg, Germany

Pyroelectric crystals are used in many optical devices, therefore, understanding the structural defects is helpful to control optical and electrical properties. It is easy to incorporate hydrogen in air-grown LiNbO₃ and LiTaO₃ crystals, however, the exact processes are only partially understood. The incorporation of hydrogen in the two materials is investigated crystal axis resolved and polarization-dependent by FT-IR spectroscopy. In the congruent material systems the hydrogen defect causes an OH band with several sub-bands, at different spectral positions for both materials.
The examined congruent crystals are cube shaped, cut and polished along the [001], [100] and [110] directions. The OH band show a significantly weaker signal for the [100] and [110] directions than for the [001] direction of the crystal cubes. Further measurements were made in the far infrared range. The aim of the crystal axis resolved and polarization-dependent study is the development of a structural model for the orientation of the OH defects of the two pyroelectric materials.