Limiting Current-type Gas Sensor Using a High Temperature-type Proton Conductor Thin Film

A limiting current-type gas sensor was composed using a thin film of the high temperature type proton conductor, CaZr0.9In0.1O3-a. The perovskite structure film was obtained by sputtering in Ar and a heattreatment at 900°C in air. A hydrogen concentration cell with this film showed theoretical EMF's at the temperatures from 500°C to 700°C. Therefore this film was regarded as a proton conductor. The film also showed a conductivity of 7×10−5 S cm−1 at 700°C in hydrogen atmosphere. The limiting current type gas sensor was composed by laminating Pt films and the proton conductor film on a alumina porous substrate. The sensor showed limiting current characteristic corresponding to partial pressures of H2, C3H8 and CO. A linear relationship was obtained between the limiting current and partial pressure of these gases.