Toluene sensing properties of YSZ-based gas sensors attached with Au-based electrodes prepared by a drop-coating method

CeO2-added Au films were drop-coated on a YSZ film fabricated on an alumina substrate embedded a Pt heater on the back side as sensing electrodes (SEs), and their toluene sensing properties were examined in dry air at elevated temperatures (400–600 °C). The suitable addition of polyvinyl alcohol in the precursor solution for drop-coating improved the roughness of the obtained film. The sensor using a 8 wt% CeO2-added Au SE showed relatively larger toluene responses at higher temperatures (450–600 °C), and the toluene response of the sensor at 500 °C was the largest (ca. 167 mV to 50 ppm toluene) among all sensors in the whole temperature range. The toluene-sensing mechanism of the sensors was discussed on the basis of the mixed potential theory. In addition, we explained that the mixed potential appeared at the interface between SE and gas [SE(Au/CeO2)/gas] in the SE layer as well as the interface on the YSZ (SE/YSZ/gas) in this study.