Highly sensitive NH3 sensor using Pt catalyzed silica coating over WO3 thick films

Ammonia gas sensing properties of a single layer WO3 thick film and a double layer sensor structure having a supported catalyst on it have been investigated. The single layer sensor exhibited low response to NH3. An enhancement in gas response was achieved by doping WO3 with Pt, Pd or Au. Ammonia sensing properties of the WO3 thick film was improved markedly by overcoating a platinum catalyzed silica-niobia layer onto the WO3 film surface. Such a double layer structure not only increased the gas response, but decreased the response time also.