Ammonia sensor based on NASICON and Cr2O3 electrode

A compact tubular sensor based on NASICON (sodium super ionic conductor) and porous Cr2O3 sensing electrode was designed for the detection of ammonia. The sensor gave excellent sensing properties to 50–500 ppm ammonia in air at 250–450 °C. The EMF value of the sensor was almost proportional to the logarithm of ammonia concentration, the sensitivity (slope) was −89 mV/decade at 350 °C. It was also seen that the sensor showed a good selectivity to ammonia, and an excellent resistance to water vapor. The sensor had speedy response kinetics to ammonia, the 90% response time to 50 ppm ammonia was 30 s, and the recovery time was 60 s.