Highly sensitive and selective ammonia gas sensor

We have fabricated and examined an ammonia gas sensor with high sensitivity using thick-film technology. The sensing material of the gas sensor is FeO_x-WO₃-SnO₂ oxide semiconductor. The sensor exhibits resistance increase upon exposure to low concentration of ammonia gas. The resistance of the sensor is decreased, on the other hand, for exposure to reducing gases such as ethyl alcohol, methane, propane and carbon monoxide. We have proposed and investigated a novel method for detecting ammonia gas quite selectively by using a sensor array with two sensing elements which contains an ammonia gas sensor and a compensation element. The compensation element is a Pt-doped WO₃-SnO₂ gas sensor which shows an opposite direction of resistance change in comparison with the ammonia gas sensor upon exposure to ammonia gas. Excellent selectivity has been achieved using the sensor array with two sensing elements