Role of the synthesis of nanopowders in the gas sensing behavior of metal oxides

The atmospheric pollutant monitoring is a present need that pushes the development of reliable and cheap solid-state gas sensors. Very small concentrations of pollutants are able to dramatically deteriorate air quality, thus atmospheric monitoring methods should be able to evaluate very low gas concentration levels. Aim of this work is to compare the sensing performances of metal-oxides powders obtained by means of sol-gel (SG) and hydrothermal (HY) method. TiO2 and SnO2 are two of the most common materials able to sense gases upon variations of their energy barrier. One of the main factors enhancing the detection properties of these oxides is the grains dimension. Sharp increase in sensitivity is in fact expected when the grain size becomes smaller than the space charge width. The work is focused on the different methodology and on the outcome related to the two methods. The properties of TiO2 and SnO2 are investigated either as powders or as thick layers, the latter necessary to prepare thick film gas sensors. © 2007 Materials Research Society.