Abstract: 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 1073K 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. [Copyright &y& Elsevier]