Charge carrier relaxation in solid VO•• conductors

The electrical properties (impedance and electric conductivity) of various VO•• conductors have been investigated in broad frequency (from 10 Hz to 3 GHz) range and wide temperature (from ambient to 1000 K) interval by impedance spectroscopy methods. Two different impedance spectroscopy techniques were used for measurements of electrical properties. Investigations in low frequency range (from 10 Hz to 2 MHz) were performed by 2-electrode method. Corresponding investigations in the high frequency range (from 0.3 MHz to 3 GHz) were based on coaxial waveguide technique. s allowed us to consistently explore peculiarities of dispersion of electrical properties attributed to charge carrier relaxation. Lightly depressed semicircular shape of relative impedance arcs was observed in complex plane plots, which was assumed as a consequence of existence of a distribution of relaxation times. This phenomenon was studied in more detail examining experimental data and numerically solving integral equation (Fredholm integral equation of first kind) for obtaining the distribution of relaxation times (DRT) function. Analysis of measured data revealed minor DRT function narrowing with temperature increase for all the investigated compounds.