Strontium titanate ferrite solid solutions are reported as potential resistive oxygen sensors for automobile application due to its zero temperature coefficient of resistance between 700 to 900 C and strong sensitivity to oxygen partial pressure. In this contribution, the oxygen sensing properties of strontium titanate ferrite at lower temperature range (<= 450 degrees C) were characterized. SrTi0.8Fe0.2O3-delta (STF20) were synthesized and fabricated into gas sensing devices using modified sol gel composite film method. Two different synthesis methods, namely high-energy ball milling and conventional high-temperature solid state reaction, were investigated and compared. The crystal structure, microstructural properties and oxygen sensing properties of the synthesized STF20-based sensing devices were characterized using X-ray diffraction, scanning electron microscope, and gas sensing measurements. High-energy ball milled STF20 was found to be milled down to around 14 nm, which is much smaller than powders prepared by solid state reaction. High-energy ball milled STF20 device showed better sensing response to 20% oxygen with optimal relative resistance of 159 at around 300 C:. The oxygen partial pressure dependency of the conductivity was also investigated. Improved 1/m value confirmed its excellent performance as oxygen sensors due to extra oxygen defects induced by high-energy ball milling process.
