Dresden 2009 – wissenschaftliches Programm

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DF: Fachverband Dielektrische Festkörper

DF 9: Glass II

DF 9.6: Vortrag

Dienstag, 24. März 2009, 15:40–16:00, WIL B321

Relaxational dynamics of a fragile plastic crystal investigated by dielectric spectroscopy — •Thomas Bauer, Melanie Köhler, Peter Lunkenheimer, and Alois Loidl — Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, 86135 Augsburg, Germany

In the present contribution, we report dielectric spectra on 60succinonitrile-40glutaronitrile (60S40GN), a binary mixture showing an orientationally disordered (OD) plastic-crystal phase with unusually high fragility [1].

Based on earlier works [2], the relaxation dynamics of OD materials generally seem to show rather strong characteristics within the strong-fragile classification scheme by Angell. However, the plastic crystalline phase of 60S40GN behaves unconventional in this respect and can be characterized as fragile [1]. This finding may be ascribed to a higher density of minima in the potential energy landscape, caused by substitutional disorder effects. Furthermore, the presented system is a good ionic conductor, showing decoupling between rotational and translational dynamics. In addition, while most other plastic crystalline phases show no or only a very weak secondary process [2], 60S40GN exhibits a well developed β relaxation.

[1] F. Mizuni, J.-P. Belieres, N. Kuwata, A. Pradel, M. Ribes, and C.A. Angell, J. Non-Cryst. Solids 352, 5147 (2006).

[2] See, e.g., R. Brand et al., Phys. Rev. Lett. 82, 1951 (1999); R. Brand et al., J. Chem. Phys. 116, 10386 (2002).