Exploration of Highly Sensitive Oxide Semiconductor Materials to Indoor-Air Pollutants

Abstract

Recently, the number of people taken ill in new house by indoor-air pollution, is steadily increasing. The phenomenon is what is called “sick house syndrome”. Mostly it is caused by formaldehyde and VOC (Volatile Organic Compound) included in adhesive or paint. The development of a sensor system available to measure the indoor-air pollution level at high sensitivity is highly desired. The present work was carried out for searching highly sensitive oxide semiconductor materials to formaldehhyde, xylene, toluen. Among 23 metal oxides examined, SnO₂, WO₃, In₂O₃, ZnO, Co₃O₄ and Cr₂O₃ showed relatively high sensitivity. Formaldehyde could be detected with excellent sensitivities by both SnO₂ and In₂O₃ elements operated at 350°C. The high sensitivity to xylene and toluene was achieved by both WO₃ and In₂O₃ elements operated at 350°C. Further, the sensing property of SnO₂ element to formaldehyde was extremely improved by the addition of Ag, and that of In₂O₃ one to xylene or toluene was also largely improved by the addition of Pd.