Fabrication & characterization of SrTiO/sub 3/ oxygen sensor operating at very low temperature

SrTiO/sub 3/ oxygen sensor were fabricated from synthesized SrTiO/sub 3/ and commercial SrTiO/sub 3/ using high-energy ball milling and the thick-film screen-printing techniques. The particle sizes, microstructural properties and oxygen sensing properties of the synthesized nano-structured SrTiO/sub 3/ oxygen sensor were characterized using X-ray diffraction (XRD) and gas sensing measurements. Experimental results showed that particle size of the powders were milled down to be around 20 nm. The effect of different annealing temperatures (400, 500, 600, 700 and 800/spl deg/C) on the gas sensing properties of the synthesized SrTiO/sub 3/ sensor to 20% oxygen was characterized. The commercial SrTiO/sub 3/ (with milling 0 hours and 120 hours) devices, annealed at 400/spl deg/C, were used as reference. The optimal relative resistance (R/sub nitrogen//P/sub oxygen/) value of 6.35 is obtained for the synthesized SrTiO/sub 3/ sample annealed at 400/spl deg/C and operating at 40/spl deg/C. This operating temperature is much lower than that of the normal low temperature metal oxide semiconducting oxygen gas sensors(300-500/spl deg/C) and SrTiO/sub 3/ oxygen gas sensors (>700/spl deg/C). The response and recovery times are 1.6 minutes and 5 minutes respectively. This is considered fast for near-room temperature operated sensor device. The detected range is 1-20% oxygen. This is a very wide range possible for a single type of sensor material.