Regensburg 2007 – scientific programme
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DF: Fachverband Dielektrische Festkörper
DF 4: Internal Symposium “Order/Disorder versus/with Displacive Behaviour”
DF 4.3: Talk
Tuesday, March 27, 2007, 11:00–11:20, H11
Peculiarities in the dielectric and heat capacity responses of strontium barium niobate — •Jan Dec1, Zdravko Kutnjak2, Severyn Miga1, Wolfgang Kleemann3, George Cordoyiannis2, Vladimir Shvartsman3, Tadeusz Łukasiewicz4, and Marek Świrkowicz4 — 1Institute of Physics, University of Silesia, Pl-40-007 Katowice, Poland — 2Josef Stefan Institute, P. O. Box 3000, SV 1001 Ljubljana, Slovenia — 3Angewandte Physik, Universität Duisburg-Essen, D-47048 Duisburg, Germany — 4Institute of Electronics Materials Technology, Pl-01-919 Warsaw, Poland
The ferroelectric materials SrxBa1-xNb2O6 (SBN) are particular among ferroelectrics since investigations of the c-axis linear dielectric response of SBN single crystals with x = 0.40, 0.50, 0.61 and 0.75, (SBN40, SBN50, SBN61, SBN75) reveal a crossover from conventional ferroelectric (SBN40) to relaxor (SBN75). The temperature dependencies of the dielectric susceptibility were measured in the range 10-2 - 10-5 Hz. Analysis of the data shows that the Curie point TC of SBN40 lies on a linear extrapolation of the "estimated" TC*s of the other SBN crystals. Correspondingly, a change from "normal" domains (SBN40) to smaller ones with fractal-like boundaries was observed by piezoresponse microscopy. The estimated TC*s correspond with anomalies in heat capacity runs. A difference in these around TC shows a non-vanishing latent heat. This complies with the positive sign of the third order nonlinear dielectric susceptibility which decreases when increasing the amplitude of the probing field. Thus, the phase transition in SBN is first order and converts into critical at higher fields.