Berlin 2015 – scientific programme

Parts | Days | Selection | Search | Updates | Downloads | Help

KR: Fachgruppe Kristallographie

KR 2: Poster Crystallography

KR 2.5: Poster

Monday, March 16, 2015, 19:00–21:00, Poster C

Kinetics of the hydrogen defect 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, 09596 Freiberg, Germany

LiNbO₃ and LiTaO₃ crystals are used in many optical devices, therefore, understanding the structural defects is helpful to control optical and electrical properties. The incorporation of hydrogen in the two materials is investigated by FT-IR and UV/VIS spectroscopy using different crystallographic orientations and excitation polarisations. The aim of the study is the development of a structural model for the kinetic and the diffusion of the OH defect. The examined congruent crystals are cube shaped, cut and polished along the [2110], [0110] and [0001] directions. The used stoichiometric crystals are plates, polished and cut in [0001]. Depending on the stoichiometry the hydrogen defect causes an OH band with several sub-bands, at different spectral positions. In congruent material two sub-bands are detectable, whereas near stoichiometric material exhibits four. The composition of the OH band with respect to formation or decline of sub-bands under oxidizing and reducing conditions shows the transport mechanisms within the crystals. The protonation in hot water shows a formation of new sub-bands at higher energies. We have found three and six sub-bands in congruent and near stoichiometric crystals, respectively. The results show that the hydrogen is disordered and can migrate to different binding sites within the crystal.