Nanostructured ceramic materials exhibit a wide range of technological applications. Particularly, they have acquired increasing importance in so highly topical fields as fuel cells and gas sensors. Impedance spectroscopy technique has become an essential tool in the correlation or the micro and nanostructure characteristics of polycrystalline ceramic materials with their electrical properties.
In the analysis of the spectral response of a sample, it is used the so called "brick layer model", which assumes a simplified microstructure composed of cubic-shaped grains. J. Fleig [1] showed a disagreement between the ideal model and the results of simulations performed in samples with a random grain size distribution. In the present work, a systematic study of the influence of particle size distribution on the impedance arcs has been carried out. Spectral response of computer generated images representing polycrystal with various microstructure distributions have been simulated. The calculations consisted on the direct resolution of kirchoff equations in the nodes of a 2D square grid superposed on the simulated image of the polycrystal. The impedance associated to each node consists on a resistance and a capacitance connected in series, taking different values when located in a point of the bulk (R_BULK , C_BULK) or of the grain boundary (R_GB, C_GB). The validity of the brick layer model for the correct interpretation of impedance spectra is discussed as a function of grain size distribution and the R_GB/R_BULK ratio.

1. J. Fleig, Solid State Ionics 181-193 (2002) 150.

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