Ammonia sensors based on stabilized zirconia and CoWO4 sensing electrode

A series of tungstate MWO4 (M = Co, Zn and Ni) has been prepared by the polymeric precursor method. Meanwhile, yttria stabilized-zirconia (YSZ) based sensors using these oxides as sensing electrodes were investigated, and among the oxides tested, CoWO4 was found to be the most suitable for the sensing electrode (SE) of the ammonia sensor. The sensor attached with CoWO4 shows the fast response and recovery characteristics (not more than 5 s respectively) and large sensitivity (− 51 mV/decade) at elevated temperature. The electric potential difference (∆V) of the sensor varies almost linearly with the NH3 concentrations in the examined range of 50–1000 ppm. The SEM observation reveals that the special microstructure of CoWO4-SE, bulky rod-like crystals coated by tiny particles, plays a significant role in sensing performance.