DIELECTRIC RESPONSE PECULIARITIES OF Ca3Ga2Ge3O12 AND Ca3Ga2Ge4O14 CRYSTALS

摘要

The studies of temperature-frequency behaviour of real and imaginary parts of electrical conductivity and dielectric constant in Ca$_{3}$Ga$_{2}$Ge$_{3}$O$_{12}$ and Ca$_{3}$Ga$_{2}$Ge$_{4}$O$_{14}$ single crystals are carried out. Experimental results were obtained in the frequency $10-10^5$ Hz and temperature 295-520 K ranges for different crystallographic axis. The frequency dependencies of electrical conductivity are explained in the polaron mechanism frame. The rise of the exponential quantity of frequency dependence conductivity in both investigated crystals at high frequencies is attributed to the increase of the phonon-free contribution to conductance. In the case of Ca-Ga-Ge-garnet oscillation structure on the curve of an imaginary part of the dielectric constant frequency dependence is connected with dipole associates such as dipolons appearing pair anion and cation vacancies coupled by electrostatic interaction. An anomalous temperature behaviour of the dielectric constant of crystals is induced in particular by charge carriers hopping between defects and initiation in addition to semi-dipoles and in the Ca-Ga-germanate case by some features of the structure.