High Ammonia Sensitive Semiconductor Gas Sensors with Double‐Layer Structure and Interface Electrodes

Ammonia gas sensing properties of a single‐layer doped with 5 mole percent (m/o) (5 m/o) sensor and some double‐layer sensors with a catalyst layer on it have been investigated. The single‐layer sensor with electrodes at the innermost region exhibited low sensitivity due to interference from produced as a result of complete oxidation of , especially at temperatures higher than 530°C. A slight enhancement in sensitivity was achieved by coating the (5 m/o) sensing layer with a catalyst layer. A more remarkable sensitivity enhancement was realized by changing the electrode position of double‐layer sensors from the innermost to the interface between the sensing and the catalyst layer, especially when loaded with 0.5 weight percent Ir was employed as a catalyst layer. Based on the catalytic activity of the sensing and the catalyst materials, possible sensing mechanism of sensors is discussed.