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Dielectrics
Ion conduction and space-charge polarization processes in Li$_2$Ge$_7$O$_{15}$ crystals
M. D. Volnyanskii,
S. N. Plyaka,
M. P. Trubitsyn,
Yahia A. H. Obaidat Dnepropetrovsk National University
Abstract:
The electrical properties of a lithium heptagermanate (Li
$_2$Ge
$_7$O
$_{15}$) crystal have been studied in DC and AC measuring fields at temperatures from 500 to 700 K. In a DC field, a substantial decrease of electrical conductivity
$\sigma$ with time has been detected. On the basis of kinetic dependences
$\sigma(t)$, estimates of the charge carrier diffusion coefficient
$D$ have been obtained. In the frequency range 10
$^1$–10
$^5$ Hz, the spectra of complex impedance
$\rho^*(f)$ have been measured. The analysis of diagrams in the complex plane
$(\rho''-\rho')$ has been performed within the equivalent circuit approach. It has been shown that, in the considered temperature and frequency intervals, the electrical properties of Li
$_2$Ge
$_7$O
$_{15}$ crystals have been determined by the hopping conduction of interstitial lithium ions
$A_{\mathrm{Li}}$ and accumulation of charge carriers near the blocking Pt electrodes.
Received: 02.08.2011
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