Nanosized Metal-Oxide Semiconducting $\hbox {SrTi}_{1 \pm x}\hbox {O}_{3 - \delta }$ Oxygen Gas Sensors for Low-Temperature Application

The X-ray diffraction and transmission electron microscope results show that nanosized-SrTi_1plusmnxO_3-delta material series (27 nm) with perovskite structure can be synthesized using the high-energy ball milling technique. The thick-film screen-printed nanosized-SrTi_1plusmnxO_3-delta-based sensor series with annealing temperature of 400 degC are found to have good oxygen-sensing property at near human-body temperature for the first time for such a low temperature. The effect of the deviating stoichiometry of the nanosized-SrTi_1plusmnxO_3-delta -based sensors on their sensing properties was also investigated. The optimal relative resistance (R_nitrogen/R_20%oxygen ) value of 6.35 was obtained by a nanosized-SrTiO_3-delta -based sensor at 40 degC operating temperature. Their near human-body operating temperature is much lower than that of the conventional low-temperature semiconducting oxygen gas sensors (300degC-500degC) and SrTiO₃ oxygen sensors (>700degC). This can extend the application of the semiconducting oxygen gas sensors from the conventional high and medium temperature to the lower operating temperature areas such as the medical, environmental, and domestic fields, etc