Berlin 2005 – wissenschaftliches Programm

Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe

DF: Dielektrische Festkörper

DF 4: Poster

DF 4.15: Poster

Samstag, 5. März 2005, 08:30–16:30, Poster TU C

Dielectric Spectroscopy of Glass Behaviour in Mixed Betaine Phosphate/Betaine Phosphite Crystals — •Juras Banys¹, Georg Voelkel², Carola Klimm², and Jan Macutkevic¹ — ¹Faculty of Physics, Vilnius University, Sauletekio 9, Vilnius 10222, Lithuania — ²Fakultaet fuer Physik, Universitaet Leipzig, Linnestr 5, Leipzig D - 04103, Germany

The complex permittivity of mixed protonated and deuterated crystals BPx/BPI1-x (with x = 0.15 to 0.5) has been studied in a wide frequency range (20Hz-1MHz). The distribution of relaxation times have been obtained directly from dielectric spectra. The parameters of the double-well potentials of the hydrogen bonds, the local polarization distribution function and the glass order parameter have been extracted from the distribution of relaxation times. An unusual result is that in contradiction to usual proton glasses the average of asymmetry A0 of the local potentials of the hydrogen bonds is nonzero, and does disappear only at low temperatures. The nonzero average of the local polarization asymmetry can be interpreted as result of a finite average cluster polarization which is averaged out at macroscopic scale. The cluster nature is unknown up to now. The new interesting result from dielectric spectroscopy is the vanishing of this cluster polarization at low temperatures. One could suspect that this disappearance of the cluster polarization is related with the real glass transition into the low-temperature nonergodic glass phase. One can conclude that the glassy behavior of the quasi-one dimensional protonated and deuterated mixed crystals BPx/BPI1-x is qualitatively different from that one in KDP-type orientational glasses.