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

Thick films of LaFeO3 and SmFeO3 were fabricated by screen-printing technol ogy on alumina substrates with comb-type Au electrodes. The perovskite-type oxide powders used for the preparation of the thick films have been prepar ed 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-sensitiv e 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 fie ld tests, the prototype sensors have been placed beside a conventional stat ion for environmental monitoring. The electrical response of the thick film s has been compared with the results of the analytical instruments for envi ronmental monitoring. The same trend was observed for both systems, with ve ry promising results. (C) 1999 Elsevier Science S.A. All rights reserved.