Low Temperature Physics: 33, 276 (2007); https://doi.org/10.1063/1.2719967 (4 pages)
Fizika Nizkikh Temperatur: Volume 33, Number 2-3 (February 2007), p. 369-373 ( to contents , go back )
Impedance of the semiconducting clathrates Sn24P19.3BrxI8-x
A.V. Yakimchuk, J.V. Zaikina, L.N. Reshetova, L.I. Ryabova, D.R. Khokhlov, and A.V. Shevelkov
The Moscow State University M. Lomonosov Faculty of physics of low temperatures and superconductivity, Moscow, 119992, Russia
Received September 7, 2006
The temperature and frequency dependences of real and imaginary parts of the impedance have been investigated for ceramic samples of clathrates Sn24P19.3BrxI8-x of variable composition at temperatures from 4.2 to 200 K in a frequency range of 20 to 106 Hz. The conductivity of the samples measured in the DC regime at T = 4.2–300 K is characterized by an activation behavior. The activation energy rises monotonously from 18 to 77 meV with an increase in Br content x. The impedance spectra are analyzed by the graphoanalitical method. The equivalent circuit used for approximation was chosen as connected in a parallel RC circuit with the frequency dependent capacitance. It is shown that a temperature drop below 75 K and a frequency rise above 150 kHz result in a rapid reduction of the capacitance contribution to the conductivity value. The dielectric anomalies observed are attributed to the significant contribution of the grain boundaries to the complex conductivity.
PACS: 71.20.Nr Semiconductor compounds;
Key words: clathrates, impedance, grain boundaries.