Response properties of resistive oxygen sensors using Ce1−xZrxO2 (x = 0.05, 0.10) thick films in propane combustion gas

Sensing properties of resistive oxygen sensors using zirconia-doped ceria were investigated in a model gas of the exhaust gas prepared by propane combustion. Resistance of the thick film of the sensor was measured as a function of excess oxygen factor (λ = C(O2)/{5C(C3H8)}, C(O2): oxygen concentration and C(C3H8): propane concentration) and temperature. The resistance of the sensor dramatically changed on λ = 1 by 1.5–2.5 orders of magnitude, and the resistance showed high and low in the lean and rich region, respectively. The temperature dependence of the resistance at λ = 0.9 (rich region) was smaller than that at λ = 1.1 (lean region). It was revealed that the sensor could detect whether exhaust gas is rich or lean in the temperature range from 723 to 1073 K without temperature compensation. When the atmosphere was alternately changed between λ = 0.9 and λ = 1.1, the resistances in rich or lean were almost the same, respectively. The results of the experiment for the sample heated by the self-heater were in accord with that heated by the furnace. It was demonstrated that the sensor using a CeO2–ZrO2 thick film could be used as a λ sensor, which can detect whether the exhaust gas is rich or lean region.