Dresden 2009 – wissenschaftliches Programm
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DF: Fachverband Dielektrische Festkörper
DF 2: Dielectric Spectroscopy & Microscopy
DF 2.6: Vortrag
Montag, 23. März 2009, 12:20–12:40, WIL A317
k-space spectroscopy on calcium barium niobate single crystals — •Urs Heine1, Uwe Voelker1, 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 report on domain size distributions in the uniaxial ferroelectric tungsten bronze type calcium barium niobate(CBN). Using noncollinear quasi-phase matched second harmonic generation (k-space spectroscopy), we are able to monitor size-dependent changes in the ferroelectric domain structure of the sample under external electric fields and in the vicinity of the ferroelectric phase transition. [001]-oriented transparent and colorless single crystals were grown by the Czochralski method with dimensions of 12 mm in diameter and about 80 mm in length. With its relatively high Curie temperature of about 538 K for 28.1 mole % calcium and its high nonlinear coefficients, CBN is a promising material for future applications. Thus, a detailed knowledge of ferroelectric properties is desirable. Our results reveal a qualitatively similar behaviour compared to the previously investigated relaxor ferroelectric SBN. The domain characteristics during polarization switching and the decay of large domain structures in the vicinity of the phase transition are clearly detectable. Directing the fundamental light beam parallel to the crystallographic c-axis leads to a characteristic cone of second harmonic light which also has been observed in SBN before. The properties of this cone, depending on the poling state of the crystal, have also been investigated.