Zeolite cover layer for selectivity enhancement of p-type semiconducting hydrocarbon sensors

Screen-printed thick films of the p-type semiconducting materials family SrTi1-xFexO3-delta have been investigated for hydrocarbon sensing. Among the different compositions tested, the formulations containing 10 and 20% of iron are found to perform best for this purpose. A pronounced cross-interference of NO persisted at operating temperatures of about 400 degrees C. In Order to eliminate this problem, the application of a zeolite cover layer was studied. The properties of this cover layer were optimized with respect to layer thickness and Pt content. Using initial results of a catalytic study on the zeolite powder in addition to a simple diffusion-reaction model, the effect of the zeolite layer with respect to NO cross-interference could be explained satisfactorily. (C) 2008 Elsevier B.V. All rights reserved.