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V 2 O 5 -WO 3 -TiO 2 mixed metal oxide catalyst was synthesized by impregnation method for fabricating sensing electrodes of potentiometric ammonia sensor in this paper. The sensing electrodes were sintered from 650 °C to 900 °C to obtain different electrode microstructures. Crystalline structures of the sensing materials were analyzed by X-ray powder diffraction, and the sensing electrode microstructures were characterized by environmental scanning electron microscopy. Sintering temperature strongly affects the microstructure and the sensitivity of the sensing electrode. With the increment of sintering temperature, the slope of semi-logarithmic characteristic curves increased but began to fall when temperature was more than 750 °C. The effect of sintering temperature on the response and recovery property has similarities, the sensors sintered at 750 °C and 700 °C show the shortest response/recovery times. The increase of the sintering temperature is beneficial for a stronger bond between sensing electrode and YSZ electrolyte, and this could increase the amount of three-phase boundary, and improve the sensor performance. High temperature promotes the V 2 O 5 volatilization, anatase TiO 2 grains growing up and the anatase to rutile phase transition, further cause the reduction of the electrode specific surface area. The volatilization of V 2 O 5 and the destruction of high dispersion V 2 O 5 resulted from the growing up of the carrier TiO 2 , are responsible for the degraded properties of sensing electrode. The suitable operating temperature for this type NH 3 sensor is 550 °C based on the compromise of various factors which could influence the sensor performance. [ABSTRACT FROM AUTHOR]

Mixed potential ammonia sensors based on 5YSZ (ZrO 2 doped 5 mol% Y 2 O 3 ) were prepared, with ferrite CoFe 2 O 4 as sensing electrode material. Co-sintering of electrode and electrolyte has been realized. Sensors with different electrode microstructure characterized by Environmental Scanning Electron Microscope (ESEM) were made by different sintering process, and its influences on the sensors’ performance were investigated. The co-sintered sensor, with a porous three dimensional network structure electrode and great adhesion with electrolyte, exhibits the largest response (about 81 mV for 320 ppm NH 3 ) and the highest NH 3 sensitivity (55 mV/decade) with the response time (8–10 s) and recovery time (10–12 s) at 450 °C, it also shows satisfying NH 3 selectivity compared with NO x , and O 2 has few influence on the sensor responses. The enhancement of the NH 3 sensitivity may owe to the porous three dimensional network structures, which is beneficial to adsorption and diffusion of the target gas, and better bonded interface between the electrode and electrolyte also provides more quantity of triple-phase boundary (TPB). [ABSTRACT FROM AUTHOR]