With a sol-precipitation method starting from WCl6, nanosized WO3 powders were synthesized.
The dependence of the powder crystallinity and microstructure on the calcinations temperature
were investigated. The WO3 phase was observed above 300 ◦C, and the mean particle size was 30
nm for 500 ◦C and 70 nm for 700 ◦C. These nanopowders were used for the pastes of porous thick
films to measure their electrical properties in air and NO2. The particle size of the powder strongly
influenced the electrical properties of the WO3 thick films. A slight increase in the NO2 response
was observed for the films prepared with powders with larger particle sizes. Much larger response
transients to different NO2 concentrations were observed for films with smaller grain sizes