SAW NOX GAS SENSOR USING WO3 THIN-FILM SENSITIVE COATING

A surface acoustic wave (SAW) delay line has been implemented onto a 1 28 degrees YX-LiNbO3 piezoelectric substrate as gas sensor. WO3 thin f ilms have been deposited by reactive rf sputtering onto the SAW propag ation path as gas sensitive coating. The SAW sensing element detects N O and NO2 in dry air in the gas concentration range 0-4400 ppm and 0-1 00 ppm, respectively, and in the temperature range 100-250 degrees C. The SAW phase response towards NOx is higher than that of two main int erfering gases, such as CO and CH4. Preliminary results on the sensing characteristics of the SAW NOx gas detector based on WO3 thin films a re reported and discussed. (C) 1997 Elsevier Science S.A.