Regensburg 2010 – wissenschaftliches Programm
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DF: Fachverband Dielektrische Festkörper
DF 13: Poster II: Electrical, mechanical and optical properties, nonlinear dielectrics
DF 13.11: Poster
Mittwoch, 24. März 2010, 15:00–17:30, Poster A
The influence of external electric fields on ferroelectric domain lengths in Calcium Barium Niobate — •Urs Heine1, Klaus Betzler1, Manfred Burianek2, and Manfred Muehlberg2 — 1Department of Physics, University of Osnabrueck, D-49069 Osnabrueck — 2Institute of Crystallography, University of Cologne, D-50674 Cologne
We present optical investigations on the novel tungsten bronze type Calcium Barium Niobate (CBN). Using the Czochralski method, [001]-oriented colorless single CBN crystals were grown from the congruently melting composition of 28.1 mole% calcium. The samples with 12 mm in diameter and about 80 mm in length were cut to 2 - 5 mm thickness, and the c-faces were polished to optical quality. Water electrodes were used to connect the c-faces to a high voltage supply, while simultaneously directing an infrared laser beam parallel to the c-axis. When illuminating the crystal, a conical light pattern emerges from the back side of the crystal due to quasi-phase matched second harmonic generation (SHG). The size distribution of the ferroelectric domain structure, contributing to the quasi-phase matching process, manifests itself in the angular intensity distribution of the SHG light pattern. We investigated the field dependent angular intensity distribution, which allows for calculating back on the average domain size, and in particular the mean length of the ferroelectric domains. The influence of ferroelectric aging effects on the domain length was also observed. Monte Carlo simulations were used for fitting generated domain structures with particular mean domain widths and lengths to the measurement data.