Ammonia gas sensor using thick film of Au-loaded tungsten trioxide

Thick films of An-loaded WO3 mixed with glass frit were prepared on an alumina substrate by the printing method, and influences of film thickness, An-loading and operating temperature on the NH4 sensing characteristics were investigated. With an increase in film thickness and An-loading, the maximum sensitivity (K-m) increased, while the temperature for maximum sensitivity (T-m) decreased, An optimum film was revealed to be the 4.0 mass % Au-loaded one of a 250 mu m-thickness for the optimum operating temperature of 450 degrees C. The sensor proved excellent NH3 sensing characteristics in gas sensitivity, response transient, resistance to humidity and long-term stability when subjected to heat cleaning once a day during its operation.