Regensburg 2007 – wissenschaftliches Programm
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DF: Fachverband Dielektrische Festkörper
DF 3: Relaxor Ferroelectrics
DF 3.6: Vortrag
Montag, 26. März 2007, 16:30–16:50, H11
Surface barrier layer contacts and colossal dielectric constants in calcium-copper-titanate — •Stephan Krohns1, Peter Lunkenheimer1, Stefan Ebbinghaus2, and Alois Loidl1 — 1Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, 86135 Augsburg, Germany — 2Solid State Chemnistry, Universitiy of Augsburg, 86135 Augsburg, Germany
For tomorrows energy-storage technologies and wireless electronics, materials with high dielectric constants are in great demand. A prominent example for this kind of materials is the perovskite-related CaCu3Ti4O12 (CCTO) [1]. It shows dielectric constants up to 105 being constant over a relatively broad temperature range. The origin of the colossal dielectric constant in CCTO is controversially debated and ascribed to internal barriers (e.g. grain boundaries) or external surface effects (e.g. electrode polarisation) [2,3]. A variety of single and polycrystalline samples, subjected to different treatments, like annealing, surface polishing and surface metallization, are investigated by broadband dielectric spectroscopy. There are at least two relaxations in CCTO, the second one being connected to even higher absolute values than the first one. From our experiments we obtain strong indications for a surface related origin of both relaxation modes and the colossal dielectric constants in CCTO.
[1] C.C. Homes, T.Vogt, S.M. Shapiro, S. Wakimoto, and A.P. Ramirez, Science 293, 673 (2001). [2] P. Lunkenheimer, et al., Phys. Rev. B 66, 052105 (2002). [3] P. Lunkenheimer, et al., Phys. Rev. B 70, 172102 (2004).