Array of thick film sensors for atmospheric pollutant monitoring

Chemical routes such as sol–gel techniques and thermal decomposition of heteronuclear complexes have been used to prepare nanosized powders of n-type (SnO2, TiO2 and In2O3) and p-type (LaFeO3) semiconducting oxides. Thick film gas sensors have been fabricated using these powders, printed on laser pre-cut 96% alumina substrates, each 2×2 mm element being provided with a heater, Au interdigitated contacts and a Pt-100 resistor for controlling the operating temperature. The films have been fired at different temperatures suitable to keep the grain size at the nanometer level. Electrical responses to some major polluting gases (CO, NO, NO2 and O3) obtained in the field have been compared with international standard analytical techniques.