Synthesis of pure and loaded powders of WO3 for NO2 detection through thick film technology

Nanopowders of pure and of Mn-, Ta- and Zr-loaded (5 wt.%) WO3 were prepared and printed as thick films. Investigation of the influence of the doping on morphology, structure and gas response versus NO2 has been performed. Pure nanometric WO3 was prepared by a modified sol-gel synthesis while loading was carried out by impregnation with Mn(II), Ta(V) and Zr(IV) chlorides. Addition of Ta resulted in grain coalescence and phase transition inhibitions in the layers with respect to pure WO3 films, being the effect strongly enhanced in the films fired at 850degreesC. The Ta-doped films turned out to be the most sensitive films with a response extending down to the sub-ppm domain. (C) 2004 Published by Elsevier B.V.