EFFECTS OF ADDED TIO2 ON THE CHARACTERISTICS OF SNO2-BASED THICK-FILM GAS SENSORS

Tin oxide-based thick films were prepared by a screen printing technique for sensing hydrocarbon gases. An SnO2-based raw material was obtained by the coprecipitation method. A conductive sensing material was synthesized by SbCl5 addition to the precipitating solution. The suspension coprecipitated was dried by hot air drying which dried the material at 110-degrees-C in a gravity convection oven or by a freeze drying method. The effects of drying method on the morphology and sensing characteristics of the thick film were investigated. The addition of TiO2 to the thick film had a substantial influence on the characteristics of the films. The sensitivities of the thick film to hydrocarbon gases were enhanced by adding TiO2 to SnO2-based materials at loading rates between 3 and 5 mol.%. TiO2 was transformed from glass or anatase to the rutile structure and this phase transformation affected the gas sensitivity of the thick film. Platinum added to the raw material during coprecipitation (as H2PtCl6.6H2O) decidedly improved the sensitivities to hydrocarbon gases.