Abstract
A tin oxide based ceramic doped with ThO 2. MgO, and PdCl 2 is developed to detect the CO gas. The sensitivity of gas sensing is measured with respect to the relative resistance change in the ceramic matrix upon the introduction of the CO gas. Intermediate operating temperature is required for the gas sensing and high sensitivity is observed at 300°C. Metallic Pd is present in the sensing matrix after mixing in ethyl, while PdO shows up after sintering at 800°C. The presence of PdO enhances the CO gas sensitivity and the response rate. However, PdO tends to be transformed to Pd in the sensing process, which leads to the deterioration in the sensitivity. A postoxidation treatment at 600°C proves to be effective in retaining PdO and high sensitivity without degradation can be obtained. In addition, a model in the gas sensing process is proposed. © 1989, The Electrochemical Society, Inc. All rights reserved.