New type of ammonia/toluene sensor combining NASICON with a couple of oxide electrodes

A tubular type sensor utilizing NASICON and a couple of metal oxide sensing electrodes was designed for detecting NH3 and C7H8 simultaneously. Here, NASICON was synthesized by sol–gel process. For detecting NH3 and C7H8, C-doped C2O3 and ZnO–TiO2 were used for the sensing electrodes, respectively. Good linear correlations between the EMF values of the sensor and the logarithm of the concentrations for 50–500 ppm NH3 and 5–50 ppm C7H8 were obtained at 250–400 °C. The sensitivities of the sensor to NH3 and C7H8 were −91 and −60 mV/decade, respectively at 350 °C. Moreover, the sensor exhibited well selectivity and rapid response–recovery characteristics to NH3 and C7H8.