High-temperature oxygen sensing behavior of perovskite films on the optical fiber platform

Real time gas sensing in high temperature energy conversion devices can enable optimal and efficient operation at both component and system levels, and the optical fiber based sensing platform shows significant advantages for harsh environment applications. In this research, (La0.8Sr0.2)0.95MnO3-δ (LSM), (La0.8Sr0.2)0.95CoO3-δ (LSC) and (La0.8Sr0.2)0.95Co0.2Fe0.8O3-δ (LSCF) films with thicknesses of several tens of nm are integrated with the optical fiber sensing platform as a functional sensor layer using a finely tuned-RF sputtering system designed for the fiber substrate deposition. Oxygen sensitivities, stabilities and overall feasibilities of these representative perovskite materials on the optical fiber platform are evaluated in the solid oxide fuel cell operational temperature regime at the oxygen concentration up to 19%, relevant for in-cell cathode stream gas composition sensing through optical transmission measurement which covers visible and near infrared wavelength ranges. Various sensitivity comparisons are carried out as a function of thickness, oxide composition, and deposition conditions. In general, the LSM sensor shows a stepwise absorption response to increasing levels of O2 in a N2 background, but also exhibits relatively slow kinetics including a continuous baseline drift. In contrast, LSCF based sensors exhibited enhanced transmittance responses in O2 containing gas and a more rapid recovery and response, presumably due to the enhanced oxygen ion diffusion kinetics as compared to LSM. The results presented here are promising for the broad application areas of high temperature O2 sensor research and a concomitantly wide range of energy related applications including combustion, solid oxide fuel cells, and others.