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 fur 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 area, 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. (C) 2000 Elsevier Science Ltd. All rights reserved.