Development of Carbon Dioxide Sensor Using Semiconductive Oxide

Mariko HANADA, Kazuo ONAGA*, Hiroshi KODA, Masakazu IWAMOTO†, Masashi NISHIGUCHI†† and Tooru ONOUCHI*††

FiS Inc.; 3-36-3 Kitazono, Itami-shi 664-1891 Japan
† Chemical Resources Laboratory, Tokyo Institute of Technology; 4259 Nagatsuta, Midori-ku, Yokohama-shi 226-8503 Japan
†† Matsushita Seiko Co., Ltd.; 4017 Takagi-cho, Kasugai-shi 486-8522 Japan

Our efforts have been devoted to the development of a compact, inexpensive, durable, and reliable CO2 sensor by using semiconductive metal oxide, since the other types of CO2 detection methods such as infrared or solid electrolyte methods are expensive or unreliableDAlthough it was well known that the conductivity of SnO2 was not altered by the change in CO2 concentration, we have first found that the addition of lanthanum onto SnO2 resulted in the induction of CO2-detecting abilityDThe addition of yttrium onto the La/SnO2 element much improved the durability of the sensor. Mounting of a filter with Pt-supporting silica gel over the sensor decreased the inhibitory effects of alcohol and water in air. The interference by the temperature change was diminished by introduction of a disk with a pinhole between the sensor and the filter. The combination of these improvements with newly developed computer software for controlling the sensor enabled us to commercialize the CO2 sensor systems in 1997.


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