Study on atmosphere modification of gas sensing sensor based on tungsten oxide thick film

Gas sensing sensor based on tungsten oxide thick film has been prepared by screen printing technology using tungsten oxide powder decomposed by tungstic acid.The sensing film was reduced and oxidized in H2 and air,respectively.Effects of H2 concentration and heat treated speed on morphology,structure and CO gas sensing properties have been investigated in detail.The results indicate that the crystal grain changes to rodlike structure or tetragonal column from spherical grain,and the crystal structure has no changes.The sensitivities(Rair/RCO) increase with increasing CO concentration and measuring temperature.Compared with the sensing film without atmosphere modification,maximum CO sensitivity has been obtained after the sensing film has been reduced and oxidized in 10% H2 and air,respectively.The sensitivity to 3.8×10-5 CO has an increase of 13.3 times correspondingly.Namely,Sensitivity can be improved greatly by atmosphere modification of sensing film.