Oxide nanopowders from the low-temperature processing of metal oxide sols and their application as gas-sensing materials

SnO2, TiO2, and In2O3 sols were prepared by a chemically modified sol-gel process. By injecting the sols into a solution of two components at 160 degrees C in non-solvothermal conditions, differently crystallized products were obtained, which were finally crystallized and purified by heat-treatments at 500 degrees C. The heat-treatments did not result in remarkable grain growth, as shown by X-ray diffraction and transmission electron microscopy. The mean crystallite size in the heat-treated powders was found to range from 3.5 nm for In2O3 to 8.5 nm for TiO2. Drop-coating of the powders onto alumina substrates allowed the fabrication of gas-sensing devices. The SnO2 and In2O3 based devices were tested to NO2, displaying outstanding responses even at temperatures as low as 100 degrees C, and fast responses and recovery times. (c) 2006 Elsevier B.V. All rights reserved.