Screen-printed perovskite-type thick films as gas sensors for environmental monitoring

Thick films of LaFeO3 and SmFeO3 were fabricated by screen-printing technology on alumina substrates with comb-type Au electrodes. The perovskite-type oxide powders used for the preparation of the thick films have been prepared by the thermal decomposition at 700 degrees C of hexacyanocomplexes, Ln[Fe(CN)(6)] . nH(2)O. These powders are ultrafine, homogeneous, and free of intragranular pores. The films have been fired at different temperatures in the 750-1000 degrees C range, in N-2 and air atmospheres. The gas-sensitive electrical response of the thick films have been tested in laboratory, in environments with different gases (CO and NO2) in dry and wet air. For field tests, the prototype sensors have been placed beside a conventional station for environmental monitoring. The electrical response of the thick films has been compared with the results of the analytical instruments for environmental monitoring. The same trend was observed for both systems, with very promising results. (C) 1999 Elsevier Science S.A. All rights reserved.