Oxygen sensor with solid-state CeO₂-TiO₂ reference

Development of a miniaturized oxygen sensor with a solid-state ceria-titania reference for automotive applications is reported. The solid reference eliminates the need for an air reference, hence enabling the device to be totally exposed to the exhaust gas. The sensor consists of YSZ electrolyte, platinum electrodes, and ceria-titania reference layers. Response of the sensor was investigated in a gas mixture consisting of 94% He, 6% CO and also air at 400, 500 and 600°C. This new sensor generates a pseudo-linear ivy lean-to-rich transition response at 400°C in the lean region, while at higher temperatures a sharp transition occurs at the stoichiometric value. Oxygen depletion and oxygen charging time of the solid reference, which has a crucial effect on sensor's performance, were measured at several temperatures by replacing the atmosphere from a gas mixture consisting of 93.8% He, 6% CO, and C₂H₆ 0.2% to air. The time response of the sensor exhibited promising results for automobile applications. The new sensor exhibits variations in the voltage, from about +500 mV in a rich region to about -500 mV in a lean region, an interesting behavior not observed previously in air-referenced structures.