Berlin 2015 – scientific programme

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KR: Fachgruppe Kristallographie

KR 7: Optical and Nonlinear Optical Properties II (DF jointly with KR)

KR 7.1: Talk

Wednesday, March 18, 2015, 15:00–15:20, EB 407

Local defect structure and dielectric relaxation in LiNbO₃ single crystals — Guillaume F. Nataf, Nadège Meyer, and •Torsten Granzow — Luxembourg Institute of Science and Technology (LIST), Belvaux, Luxembourg

The defect structure of LiNbO₃ (LN) has been studied more extensively than that of most other oxide ferroelectrics for several reasons. First, congruently melting LN is already rich in defects: it is strongly Li-deficient and contains a high concentration of Nb_Li antisite defects. Second, the possibility to adjust the optical properties by doping with a wide range of ions has increased the usefulness of LN for optical applications. Third, due to the high mobility of Li at moderate temperatures, the poling procedure can have a profound influence on the local defect structure. However, few studies have considered the effect of this local structure on the dielectric properties of LN. In this presentation, the temperature dependence of the real and imaginary part of the electrical permittivity of differently doped LN single crystals is investigated in the frequency range from 1 Hz to 1 MHz. Different relaxation phenomena are caused by thermal and electrical treatment and traced to differences in the local defect structure. Ferroelectric domain walls stabilize the local defect structure. These assumptions are supported by measurements of the temperature dependence of electrical conductivity and the thermally stimulated depolarization current.