High temperature zirconia oxygen sensor with sealed metal/metal oxide internal reference

Abstract

Potentiometric internal reference oxygen sensors are created by embedding a metal/metal oxide mixture within a yttria-stabilized zirconia oxygen-conducting ceramic superstructure. Three metal/metal oxide systems based on Pd, Ni, and Ru are examined. A static internal reference oxygen pressure is produced inside the reference chamber of the sensor at the target application temperature. The metal/metal oxide-containing reference chamber is sealed within the stabilized zirconia ceramic superstructure by a high pressure (3–6 MPa) and high temperature (1200–1300 °C) bonding method that initiates grain boundary sliding between the ceramic components. The bonding method creates ceramic joints that are pore-free and indistinguishable from the bulk ceramic. The Pd/PdO-based oxygen sensor presented in this study is capable of long-term operation and resistant to the strains of thermal cycling. The current temperature limit of the device is limited at 800 °C. As the sensor does not require reference gas plumbing there is flexibility in placement of sensors in a combustion stream. Furthermore, the sensor assembly process readily lends itself to miniaturization.