Fabrication of free-standing titania-based gas sensors by the oxidation ofmetallic titanium foils

A simple method for fabricating TiO2,-based sensors of CO(g) is demonstrate d: the oxidation of Ti-bearing foils. Metallic foils (35 mu m thick) were c onverted into free-standing, porous rutile foils (60 mu m thick) by exposur e to O-2(g) at 800 degrees-965 degrees C. The oxidized foils contained thin (0.5-1 mu m thick), regularly spaced oxide layers oriented parallel to the external surface. The exposure of such porous foils to increasing concentr ations of CO(g) resulted in a monotonic increase in the steady-state electr ical resistance. Rutile foils sensitive to 50 ppm changes in CO(g) content with response times of a few minutes were produced. The effects of oxidatio n conditions and copper doping on sensing performance are discussed.