| Abstract [eng] |
Zirconia (ZrO2) and ceria (CeO2) based solid oxygen ion conductors are investigated in the dissertation. The electrical properties (impedance and electric conductivity) were studied in broad frequency (from 1 Hz to 10 GHz) range and wide temperature (from ambient to 1150 K) interval by advanced impedance spectroscopy methods. Dispersions of electrical properties, attributed to charge carrier relaxation in electrical field, were observed in the obtained spectra. These data in complex plane plots resulted to depressed semicircles, which was assumed as consequence of existence of a distribution of relaxation times of charge carrier. The phenomenon was studied in more detail by examining the frequency domain impedance data in terms of distribution of relaxation times (DRT) of charge carrier. A new algorithm for estimation of DRT function of charge carrier was developed for this purpose. Advantages of wide frequency and temperature intervals allowed to investigate the peculiarities of the DRT function’s behaviour with changes in temperature as well as dopant concentration, which were observed in single crystals, bulk and grain boundary medium of ceramics. The results showed that the DRT function of charge carrier in fluorite-structured oxygen ion conductive ceramics and single crystals may be described nearly Gaussian-shaped curve in logarithmic time scale, which narrows with increasing temperature and decreasing dopant concentration. |
