An alternative representation of impedance spectra of ceramics

Suitable approximations are derived to extract the relevant parameters of the bulk, grain boundary, and electrode contributions of impedance spectra from Z′ vs. Z″/f plots. Corrections are proposed for cases where the difference between bulk and grain boundary relaxation frequencies and/or the difference between grain boundary and electrode relaxation frequencies is relatively small. In these cases, the Nyquist plot (Z″ vs. Z′) shows overlapped arcs, but inspection of alternative Z′ vs. Z″/f representations may reveal contributions with relatively small differences in relaxation frequencies. These plots and the corresponding derivative dZ′/d(Z″/f) may be useful to interpret cases showing a significant distribution of grain boundary relaxation frequencies.