Characterization of Nano-Sized SrTi/sub 1/spl plusmn/X/O/sub 3-/spl delta// Metal Oxide Semiconducting Oxygen Gas Sensors for Near Human-Body Temperature Application

The X-ray diffraction (XRD) and transmission electron microscope (TEM) results show that nano-sized SrTi
_1plusmnx
O
_3-delta
material series (27 nm) with perovskite structure can be synthesized using the high-energy ball milling technique. The thick-film screen printed nano-sized SrTi
_1plusmnx
O
_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 nano-sized SrTi
_1plusmnx
O
_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 nano-sized SrTi
_1plusmnx
O
_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 (300-500 degC) and SrTiO
₃
oxygen sensors (<700 degC). 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