Fundamental Study on the SOX Gas Sensor Utilizing Beta-Alumina with Sputtered Praseodymium Oxide Thin Films by Shinya YAO1*, Kenji MIYAGAWA1, Shigeru IIJIMA2 and Zensaku KOZUKA1 1. Faculty of Engineering, Osaka University, Suita, Osaka 565 2. NTK Spark Plug Co., Ltd., Iwaki, Aichi 485 *Nee: OTSUKA The SOx gas sensor utilizing beta-alumina as a solid electrolyte has a rigid theoretical background and produces a reliable emf corresponding to SO2 gas partial pressure, PSO2. However, its emf response to a change in PSO 2 is not as fast as that to other electrolytes. In the present study, in order to improve the chemical properties of the surface of the beta-alumina disc, praseodymium was sputtered on both sides through a stainless steel net and oxidized in air. The SO2 gas sensor utilizing the Na+-ƒÀ"-alumina disk covered by Pr6O11 was tested at 873 and 1,023 K and compared with the performance utilizing ƒà"-alumina uncovered. There was a significant difference in the emf's at 1,023 K. The hysteresis of the emf's at 873 K with a change in PSO2 was significantly reduced by the coverage, that is, the coverage with Pr6O11 thin film improved the performance of SOx sensor at a low temperature. The Pr6O11 thin film may reduce the vaporization of Na2O from ƒà"-alumina and also the absorption of water vapor by ƒà"-alumina. In the mixtures of Pr6O11 and ƒà"-alumina powders annealed at 1,073 K, a compound was detected by means of the X-ray diffraction method with a diffractometer. The formation was very slow with time, and had an essentially negligible effect on the performance of the SOx sensor. A significant difference in the response speed was not observed. The response speed should be investigated by changing the kind of rare-earth oxide thin film. KEY WORDS: SOx Gas Sensor, Beta-Alumina, Emf Measurements, Rare-earth Oxide, Sputter, Thin Film
Fig. 1 Schematic drawing of the SOX sensor used in this study.
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