Output Evaluation of Resistive Oxygen Sensor having Ce0.9Zr0.1O2 Sensing Material and Zr0.8Y0.2O2-.DELTA. Temperature Compensating Material in Model Exhaust Gas

Abstract

We fabricated resistive-type oxygen sensors having a Ce0.9Zr0.1O2 thick film as a sensing material and a Zr0.8Y0.2O2-δ thick film as a temperature compensating material for the first time, and measured the resistance of the two thick films and the output of the sensors in model exhaust gas which was a combustion gas of propane. Then, we considered whether the sensor could be used as a “lambda sensor,” which can identify whether the air-to-fuel ratio of exhaust gas is rich or lean region. As a result, we confirmed that the resistance of the Ce0.9Zr0.1O2 thick film was low and high in the case of rich and lean regions, respectively. The activation energy of the resistance of the Ce0.9Zr0.1O2 film was 0.41 and 1.20 eV in rich and lean regions, respectively, and the mean value of them was 0.8 eV. The resistance of the Zr0.8Y0.2O2-δ thick film in rich was almost the same as that in lean. The activation energy was 0.92 and 0.98 eV in rich and lean, respectively, and similar to the mean value of the activation energies of the Ce0.9Zr0.1O2 film in rich and lean. This result shows that the combination of the Ce0.9Zr0.1O2 and Zr0.8Y0.2O2-δ films is better for the “lambda sensor.” The electrode structures of the sensor were optimized so that the mean value of the resistances of the Ce0.9Zr0.1O2 film in rich and lean was the same as the resistance of the Zr0.8Y0.2O2-δ film. The difference in output of the resistive oxygen sensor having the optimized electrode between rich and lean regions was more than 0.7 V, when the source voltage was 1.0 V. The output dramatically changed on the stoichiometric air-fuel ratio. From above-mentioned results, we conclude that the resistive oxygen sensors fabricated in this study are able to be used as “lambda sensors.”