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 thic kness, An-loading and operating temperature on the NH4 sensing charact eristics were investigated. With an increase in film thickness and An- loading, the maximum sensitivity (K-m) increased, while the temperatur e for maximum sensitivity (T-m) decreased, An optimum film was reveale d to be the 4.0 mass % Au-loaded one of a 250 mu m-thickness for the o ptimum operating temperature of 450 degrees C. The sensor proved excel lent NH3 sensing characteristics in gas sensitivity, response transien t, resistance to humidity and long-term stability when subjected to he at cleaning once a day during its operation.