Berlin 2005 – scientific programme

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DF: Dielektrische Festkörper

DF 9: Phasenüberg
änge und Spektroskopie

DF 9.7: Talk

Tuesday, March 8, 2005, 12:20–12:40, TU EMH225

Dielectric spectroscopy of CuInP₂(S_xSe₁−x)₆ ( with x=0.4-0.95) layered crystals — •Juras Banys¹, Jan Macutkevic¹, Robertas Grigalaitis¹, Algirdas Brilingas¹, and Julian Vysochanskii² — ¹Departament of Radiophysics, Faculty of Physics, Vilnius University, Lithuania — ²Institute of Solid State Physics and Chemistry of Uzhgorod University, Ukraine

The complex dielectric response of CuInP₂(S_xSe₁−x)₆ crystals were investigated in the frequency range 20 Hz to 1.2 GHz. At low frequencies and high temperatures the dielectric spectra is mainly caused by high ionic conductivity. At higher frequencies and lower temperatures the dielectric spectra is caused by a broad distribution of relaxation times. The maximum of real and imaginary parts of dielectric permittivity shifts to the higher temperatures with increasing frequency. Obtained dielectric spectra were fitted with Cole-Cole formula and the mean relaxation time has been obtained. On cooling the Cole-Cole mean relaxation time strongly increase and distribution of relaxation times broaden. The temperature dependence of mean relaxation time was fitted with Fogel-Vulcher law. All features of the dielectric dispersion at low temperatures of present crystals are typical for the dipolar glasses. In the crystals with sulfur concentration x=0.95 ferroelectric phase transition has been observed together with the glass state at low temperatures.