Impedance spectra have been analysed based on interpretation of minima of the imaginary part of impedance vs frequency. One derived useful relations and used simulated examples to illustrate how this method can be applied. The bulk relaxation frequency, bulk capacitance and grain boundary capacitance can be extracted from the values of imaginary and real impedance parts at the minimum of Z '', and corresponding frequency. The proposed relations are also used to analyse impedance spectra obtained for ceramic samples of Yb2Ti2O7-based materials. The consistency of the analysis is also examined for cases when the representation of imaginary part of impedance vs real impedance shows a significantly depressed arc. This can be interpreted as resulting from distribution of relaxation frequency values. (c) 2008 Elsevier Ltd. All rights reserved.