An impedance and electric conductivity of 10 mol%Y2O3-90 mol%ZrO2 and 15 mol%CaO-85 mol%ZrO2 single crystals were investigated in frequency range from 10 Hz to 3 GHz at temperatures from room temperature to 970 K by impedance spectroscopy methods. Investigations in the high frequency range were performed by the measurement of S-parameter matrix for a 2-port network of a coaxial waveguide and a sample, inserted in the gap of a central conductor. At the low frequencies 2- and 4-electrode methods were used for accurate measurements of the impedance and electrical conductivity. The quality of the experimental data was verified using Kramers-Kronig transforms. The obtained frequency dispersion of the electrical properties related to charge carrier relaxation in the electrical field was examined in terms of distribution of relaxation times (DRT). DRT function was obtained by numerically solving the Fredholm integral equation of first kind with newly developed Matlab application. Analysis of the experimental data has revealed slight spreading of the relaxation time distribution with temperature decrease for both single crystals. The temperature dependencies of the relaxation time corresponding to the DRT function peak showed Arrhenius behavior with activation energy close to that of electrical conductivity. (C) 2012 Elsevier B.V. All rights reserved.