Selectivity enhancement of p-type semiconducting hydrocarbon sensors—The use of sol-precipitated nano-powders

A method for preparing sol-precipitated Sr(Ti0.8Fe0.2)O3−δ powders yielding particle sizes of about 70 nm is presented. Screen-printed films based on such nano-scaled powders are compared and contrasted to conventional micro-scaled thick films.By employing sol-precipitated powders, the hydrocarbon sensitivity of the sensor devices is improved. For unsaturated hydrocarbons, resistance changes similar to those of thin films prepared by pulsed laser deposition are observed, thus combining the fast sensor response of Sr(Ti0.8Fe0.2)O3−δ thick films with the high response (R/R0) values observed for thin films. The pronounced cross-interference of NO and CO can be eliminated by means of an additional zeolite layer deposited on top of the nano-scaled sensor film.