A new type of amperometric oxygen sensor based on a mixed-conducting composite membrane

A new type of amperometric oxygen sensor has been developed in which a dense Pt-YSZ composite layer, a mixed ionic–electronic conductor (MIEC) membrane, is used as the diffusion barrier. Accelerated materials stability tests in the exhaust of a gas-fired engine indicate that yttria-stabilized zirconia (YSZ) with fluorite structure has excellent stability while the stability of La0.9Sr0.1Ga0.2Mg0.8O3 (LSGM) is questionable. A dense Pt-YSZ composite layer has been prepared on a YSZ electrolyte using nanoparticles of platinum, derived from a sol–gel process. The fabricated sensors based on a bi-layer structure, Pt-YSZ/YSZ, exhibit well-defined diffusion-limited currents for oxygen concentrations up to 6% and the current responses depend linearly on oxygen concentration. The developed sensor is anticipated to have excellent chemical, microstructural, and thermal stability because of the remarkable stability of a dense composite layer consisting of YSZ and Pt.