The Preparation And Gas-sensitive Properties Of α-Fe₂O₃Gas Sensor

In this paper, a-Fe2O3nano-powders and doped a-Fe2O3nano-powders were prepared by ultrasonic chemistry-method. The powders were characterized with the aids of XRD, TG, TEM and SEM. Effect of preparation technology on dispersity and morphology has been studied. Gas sensors were made from a-Fe2O3nano-powdes.They have been tested in CO atmosphere. This paper anaiysed the impact of microstructure and partical size on gas-sensitive property and discussed the mechanism of gas sensor.Precursor phase transforms into a-Fe2O3directly when the raw material is Fe2(SO4)3and NaOH. While the raw material is FeCl3and NaOH, precursor generates y-Fe2O3first, then γ-Fe2O3phase transforms into a-Fe2O3between450℃and500℃. The existence of SO42-restrain the growth of the iron oxide crystal. a-Fe2O3has a lower degree of crystallinty when the raw material is Fe2(SO4)3. Through the orthogonal experiment, the paper get a good preparation technology, ultrasonic power:53w, calcination temperature:500℃,calanation time:60min.1wt.%PEG2000has a good effect on the powers’decentealize.a-Fe2O3with MnO2doped can enlargy it’s partical size for50nm to100nm while Sn4+doped reduce the size for20nm to50nm. Doped Y2O3can inhibit the crystallization of a-Fe2O3. a-Fe2O3nanoparticles grown into rod when Al3+and SnO2doped. Gas sensors has been tested in CO atmosphere. Gas sensors’response time is approximate14seconds and it’s recovery time is about7seconds.the recovery time prolong with the size of the a-Fe2O3nano-powders. Gas sensors with single-phase doping have a sensitivity between1.68and2.83. sensitivity increases with the amout of doping. Sensitivity with duplex doping have a large improvement.The sensitivity reached3.27when doped with Al3+and SnO2of4%mass fraction.