Selectivity enhancement of a WO3/TiO2 gas sensor by the use of a four-point electrode structure

A new electrode structure with two additional middle-electrodes running in-between the interdigitated electrodes, is presented. With this structure, the voltage drops at these middle-electrodes are measured as well as the conductivity of a screen printed n-type WO3/TiO2, mixed oxide layer. The gas-sensing properties to NOx, CHx and CO are determined at 300 degreesC. It is shown that with this four-point structure, different sensor regions, namely the pure semiconducting layer and the interface electrode/semiconductor, can be separated and different gas-sensing properties can be determined for this regions. Additionally, by evaluating the signals at the middle-electrodes, single gases in gas mixtures can be detected and discriminated. (C) 2003 Elsevier Science B.V. All rights reserved.