Gas sensing characteristics of ZnO-doped SnO₂ sensors for simulants of the chemical agents

After the 911 terrorism and America-Iraq war, apprehension of mass destruction weapons such as bio-chemical agents calls for much more sensitive sensors which can detect toxic gases. In this study, semiconductor gas sensors based on tin oxide were examined to detect chemical agent simulants: dimethyl-methyl-phosponate (DMMP), di(propylene glycol) methyl ether (DPGME), acetonitrile, and dichloromethane. DMMP((CH₃O)₃), DPGME(C₇H₁₆O₃), acetonitrile(CH₃CN), and dichloromethane(CH₂Cl₂) gases are the simulants of nerve agent-sarin, vesicant agent-HN(N(CH₂CH₂Cl) ₃), blood agent-AC(HCN), and choking agent-CG(COCl₂) gases, repectively. The SnO₂ powder was prepared by a coprecipitation method from the mixture of tin chloride and zinc acetate dihydrate. Zinc oxide was doped into SnO₂ from 1 wt% to 4 wt% to improve its reliability and sensitivity. To fabricate a thick film, powders were made into paste with organic binder of ethyl cellulose and screen-printed on the alumina substrate. The phase development and morphology of ZnO-doped SnO₂ film were investigated by XRD (X-ray diffraction analysis), BET (surface and pore size analyzer), and SEM (scanning electron microscope). The gas sensing characteristics for target gases were examined with a flow-type measurement system. The concentrations of simulants were controlled from 500 ppb to 1500 ppb, and working temperatures were regulated from 250 °C to 400 °C.