Preparation of a porous ceria coating for a resistive oxygen sensor

Oxygen sensors play important roles in areas such as determining the oxygen content in exhaust gas and optimizing combustion. Resistive oxygen sensors made of an n-type semiconductor, doped ceria (CeO2), have recently received much attention due to their relatively compact and simple structures. In the present study, alumina substrate was first coated with electrodes by screen printing. Porous ceria films were then coated on the electrodes using different mixtures of two undoped ceria powders synthesized by spray-pyrolysis and precipitation, respectively. The ratios of the two powders were varied to produce differences in the heat-treated porosity of the ceria films. The resistive oxygen sensors exhibited a 3-D interconnected pore structure that could be optimized by varying the powder ratio for sensing properties. The dynamic response to the change in oxygen partial pressure of the optimized porous structure at 1073 and 1123 K was >1.8 times faster than those of non-optimized structures. Details on the processing, optimization of compositions, and responses to variation in oxygen partial pressure are provided. The mechanisms for the formations of the powders and the porous coatings are also described.