Limiting current type yttria-stabilized zirconia thin-film oxygen sensor with spiral Ta2O5 gas diffusion layer

In this study, we demonstrated a limiting current-type yttria-stabilized zirconia thin-film oxygen sensor with a gas diffusion layer composed of porous Pt and spiral Ta2O5, which were deposited via sputtering and rotational oblique evaporation, respectively. The rate of the oxygen gas diffusion through the porous Pt and spiral Ta2O5 films defined the limiting current level of the oxygen sensor. When evaporation angle was between 70 degrees and 84 degrees, the relative density of the spiral Ta2O5 was between 0.72 and 0.37. The microstructure of the spiral Ta2O5 film was maintained after annealing at 700. C for 1 h. The characteristics of the limiting current were clearly observed between 400 degrees C and 600 degrees C, which can be attributed to the oxygen gas diffusion rate in the spiral Ta2O5 film. The current response time was 3 s or less after applying the voltage. The level of the limiting current was directly correlated with the oxygen gas concentration. Owing to the thermally stable spiral Ta2O5 microstructure, the characteristics of the limiting current, including the limiting current level and response time, were confirmed to be consistent for up to ten cycles of temperature modulations. The oxygen gas concentration and water vapor were separately measured by applying 1.1 V and 1.8 V, respectively. The presence of CO2 and H-2 did not affect the limiting current level for its application in the atmosphere.