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DF: Dielektrische Festkörper

DF 7: Phasenüberg
änge und Spektroskopie

DF 7.4: Vortrag

Donnerstag, 11. März 2004, 15:50–16:10, H11

High frequency dielectric response of strontium barium niobate in the relaxor and ferroelectric regimes — •J. Banys¹, W. Kleemann², J. Macutkevic¹, R. Grigalaitis¹ und R. Pankrath³ — ¹Physics Department, University of Vilnius, Vilnius, Lithuania — ²Angewandte Physik, Universität Duisburg-Essen, 47048 Duisburg — ³Fachbereich Physik, Universität Osnabrück, 46069 Osnabrück

The dielectric permittivity of SBN:0.02% Co²⁺, є′ + iє″, is measured at frequencies 20 < f < 6·10⁸ Hz and temperatures 300 < T < 450 K both in the poled and unpoled state. Below T_c = 348 K the unpoled sample reveals the well-known [1] relaxation behavior of pinned domain walls [2] extending up to the highest frequencies, while a flat dispersion regime up to 10⁶ Hz and a broad step within 10⁶ < f < 10⁹ Hz characterize є′ of the unpoled sample at T > T_c and the poled sample at all temperatures. The latter behavior is also reflected by a broad peak of є″ at f = 10⁷ - 10⁹ Hz and is attributed to the relaxation of random-field pinned precursor clusters of the polarization [3]. The data are successfully described in terms of Cole-Cole and Havriliak-Negami-type dispersion relations and best-fitted to distribution functions of relaxation times, which show typical relaxor behavior.

[1] W. Kleemann et al., Phys. Rev. B 65 (2002) 220101R.

[2] T. Nattermann et al., Phys. Rev. B 42 (1990) 8577.

[3] W. Kleemann et al., Eur. Phys. Lett. 57 (2002) 14.