Resistive Oxygen Gas Sensors Using Ceria-Zirconia Thick Films

Abstract

The resistive oxygen gas sensors using CeO₂-ZrO₂ thick films with various ZrO₂ concentrations (0-60 mol% ZrO₂) were fabricated. In order to decrease emission of exhaust gas, resistive oxygen sensors need to have low resistivity, good sensitivity and fast response. The thick films were screen-printed on alumina substrate with a viscous paste, a mixture of the CeO₂-ZrO₂ powders and organic binder. The resistivity of thick film (ρ) as a sensor output, the oxygen partial pressure dependence of the resistivity (n: the parameter in ρ∝P(O₂)^1/n, where P(O₂) was oxygen partial pressure), and the response time of the thick film were investigated in detail. The thick film doped with 0.5-40 mol% ZrO₂ had a shorter response time, a lower resistivity, and a better oxygen partial pressure dependence of resistivity compared to the thick film doped without ZrO₂. Further, it became clear that the thick film doped with 10-30 mol% ZrO₂ had the best sensor property in the CeO₂-ZrO₂ thick films. The mechanism of the effect of ZrO₂ addition was also discussed.