Development of Carbon Dioxide Sensor Using Semiconductive Oxide

Abstract

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.Although 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.The 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.