Abstract: Potentiometric oxygen sensors have been widely used in internal combustion engines, industrial boilers, and metallurgical heat treatment furnaces. However, traditional oxygen sensors based on yttria-stabilized zirconia (YSZ) electrolyte can only be operated at elevated temperatures (> 750 °C) due to their relatively low ionic conductivity. In this study, we present a highly efficient micro-oxygen sensor that can be operated at a temperature as low as 300 °C. This micro-oxygen sensor incorporates a composite solid electrolyte, i.e., well-aligned gadolinium-doped cerium oxide (CGO) nanofibers embedded within a YSZ matrix (YSZ/CGO_f). The arrays of CGO nanofibers in the YSZ matrix are parallel to the conduction direction, providing rapid conducting channels for oxygen ions. Benefitting from this design, the composite electrolyte leads to a conductivity of four times higher than that of traditional YSZ solid electrolytes at low temperatures. This enhancement in conductivity is attributed to the presence of a defective interfacial region between CGO_f and YSZ, which promotes the mobility of oxygen ions. The strategy of constructing fast ionic conduction in the composite electrolyte by using well-aligned nanofibers may be considered for the design and optimization of other micro/nano-devices including sensors, batteries, and fuel cells.

Key words: Oxygen sensor, Nanofibers, Composite electrolyte, Ionic conduction