Highly sensitive mixed-potential-type NO2 sensor using porous double-layer YSZ substrate

In this article, the NO2 sensing performance of the mixed-potential-type yttria stabilized zirconia (YSZ)-based sensor was improved by modifying the three-phase boundary (TPB). The double-tape casting and the pore-forming method were simultaneously used to obtain the porous YSZ-substrate. Furthermore, a group of tape-casting slurries with different starch concentrations (0 wt%, 5 wt%, 10 wt% and 15 wt%) were applied to form the different contact areas of the three-phase boundary (TPB). The scanning electron microscope (SEM) images showed that YSZ-substrate prepared by using the slurry with 15 wt% starch had the largest contact area. The sensor based on the YSZ-substrate with the largest contact areas and the MnCr2O4 sensing electrode (SE) showed the largest response compared with the other sensors when they were exposed to 10–500 ppm NO2 at 800 °C. The measured polarization (I–V) curves indicated that the present sensors operated under the mixed-potential mechanism. In addition, the sensor showed a good selectivity and repeatability to NO2.