In this contribution, the binary ceramic system La 2 CuO 4 -LaFeO 3 is investigated for resistive oxygen sensor applications. The temperature-independent characteristics that are observed for copper contents of 30% or higher are of particular interest. In order to correlate sensor characteristics and material composition, an initial model describing the complex two-phase system is proposed. It is based on the so-called generalized effective media theory (GEMT), a useful tool for describing bi-phase composites. The fitting procedure allows to predict the actual sensor characteristics determined by the experiments.