The TiO2-adding effects in WO3-based NO2 sensors prepared by coprecipitation and precipitation method

Two different sensing materials of TiO2-WO3 system with the grain size of n anometer are synthesized; one is a complete 2-nm-sized coprecipitate ((Ti,W )O-2) made by sol-coprecipitation of TiCl4 and WCl6, and the other is a com plex 8-nm-sized material (TiO2 + WO3) by mixing the sol-precipitation of Ti Cl4 and WCl6. The TiO2-WO3 system showed different characteristics between the coprecipitate and the complex material of TiO2 and WO3. The sensitivity and sorption properties were improved in the coprecipitate. In the copreci pitate, the sensitivity defined as R-G/R-A, where R-G and R-A are resistanc e in gas ambient and in air, respectively, was about 100 for 30 ppm NO2 at 340 degrees C, which is suited for facility combustion furnace. The copreci pitated sensing materials had different resistance and grain size of 6 nm a fter calcination in air at 600 degrees C for 2 h. The properties of precurs or have been investigated by SEM, X-ray diffraction (XRD) and BET analyses. (C) 2000 Elsevier Science S.A. All rights reserved.