Oxygen sensor with solid-state CeO2–ZrO2–TiO2 reference

Development of an oxygen sensor for automotive applications with a solid-state reference is reported. Unlike conventional oxygen sensors used in monitoring exhaust gas emissions, in which one side of the sensor must be directly exposed to the air reference, the new sensor employs a ternary mixed oxide of CeO2–ZrO2–TiO2 (hereafter referred to as CZT) as the reference. The sensor consists of YSZ electrolyte and CZT reference layers with platinum coating as electrodes. The response of the sensor was investigated in a gas mixture of 6 mol% CO (in He) and air at 400, 500 and 600 °C. At 400 °C, the sensor generates a wide hysteresis in the lean region, while at higher temperatures a narrower hysteresis occurs at λ = 1. The sensor also exhibits variations in the voltage, from about +300 mV in the rich region to about −250 mV in the lean region, an interesting behavior not observed in air-referenced structures.