Oxygen Sensor Using Proton-Conductor Thick-Film Operative at Room Temperature

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Abstract
An amperometric solid-state oxygen sensor using a proton-conductor thick-film was investigated as an approach to a miniaturized and intelligent oxygen sensor operative at room temperature. The proton conductor film was formed on a porous alumina substrate by spin-coating the paste containing antimonic acid (Sb2O5⋅2H2O) and a polyvinyl alcohol (PVA) binder. The sensor element was composed of the following electrochemical cell; sputtered Pt film (counter electrode) |proton-conductor thick film (10μm)| sputtered Pt film (sensing electrode), gas-diffusion layer (40-100μm). A limiting current, controlled by oxygen permeation through the gas-diffusion layer, was observed when an external voltage over 1.4V was applied to the above cell. The limiting current (sensing signal) increased linearly with an increase in oxygen partial pressure in the sample gas up to 1.0atm at an external voltage of 1.6V. The 90% response time was about 40s for increasing oxygen partial pressure at 30°C. It was found that the sensor could also respond to dissolved oxygen in water at room temperature. With a sensor using a hydrophobic gas-diffusion layer containing a polystyrene (PS) binder, the limiting current was linear to the dissolved oxygen concentration up to 20ppm, with a 90% response time of about 9min at 30°C.

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