Impedancemetric zirconia-based sensor attached with laminated-oxide sensing-electrode aiming at highly sensitive and selective detection of propene in atmospheric air

Aiming at a sensitive and selective detection of very low concentrations of propene (C3H6) in an atmospheric air, the impedancemetric yttria-stabilized zirconia (YSZ)-based sensor was fabricated and examined. Among the different oxide sensing-electrodes (SEs) studied, SnO2-SE was found to give the highest sensitivity to C3H6 at 600 °C even in the presence of 1.35 vol.% H2O and 400 ppm CO2. Then, the selective response to C3H6 was achieved by coating of the additional oxide layer (ZnO) onto SnO2-SE, giving the laminated-type ZnO/SnO2-SE. Moreover, to improve further the sensing performances of the present sensor, ZnO powder (0–30 wt.%) was subsequently added to the SnO2 layer of the laminated ZnO/SnO2-SE. As a result, the sensor using ZnO/SnO2 (+ 20 wt.% ZnO)-SE exhibited highly selective and sensitive response to C3H6 at 500 °C with minor cross sensitivities to other co-existing gases, such as NOx, H2, CO and CH4. The sensitivity of the present sensor varied linearly with the logarithm of C3H6 concentration in the range of 20–100 ppb and was found to be hardly affected by the change in water vapor concentration.