Different thick-film methods in printing of one-electrode semiconductor gas sensors

Different thick-film printing techniques have been used for the fabrication of one-electrode semiconductor gas sensors in the form of thick films on insulating alumina substrate. In a typical one-electrode sensor construction, a thin platinum wire (diameter 20 mu m) spiral is embedded inside a sintered oxide semiconductor button. The platinum wire spiral is replaced by a platinum thick-film resistor in our prototype sensor, and the oxide semiconductor is screen printed over the platinum resistor. Both screen printing and gravure offset printing (pad printing) were used for the printing of platinum thick-film resistors. Tin dioxide, an n-type semiconductor, was used as the sensing (shunting) thick-film layer over the platinum resistor, and different amounts of either silver or antimony were used as additives in SnO2. H2S and CO at different concentrations in synthetic air were used to test the response properties of two different sensor types with, respectively, screen-printed and pad-printed platinum thick-film resistors.