Percolation conductivity in BaZrO3-BaFeO3 solid solutions

Electrical conductivity of Fe-doped BaZrO3 (BaZr1-xFexO3-delta) has been investigated to understand a percolation conduction mechanism in a single-phase oxide. The dependence of electrical conductivity on Fe concentration, x shows a strong nonlinear variation in the composition range between x = 0.2 and 0.3, which is explained by a simple cubic percolation model based on network composed of FeO6 and ZrO6 as a unit element. The most significant difference from simple composite percolation conductivity with independent conductivity elements is the fact that FeO6 works not only as a conductive component, but also as the carrier donation source to non-conductive one. Although the most holes on O2p orbital in ZrO6 matrix are trapped in FeO6 octahedera, the partial hole conduction along FeO6 percolation path prevails upon the occurrence of percolation. In the present study, a model to describe such situation is proposed and examined for numerical analyses. Low hole conductivity with a high activation energy (similar to 1.22 eV) occurs when the holes migrate over ZrO6 matrix, in contrast to higher hole conductivity with the low activation energy (similar to 0-03 eV) occurs upon formation of FeO6 percolation network. (C) 2014 Elsevier B.V. All rights reserved.