GAS-SENSING CHARACTERISTICS OF TIN DIOXIDE WITH SMALL CRYSTALLITES

The effect of calcining temperature on gas sensitivity and resistance in wet air was observed with elements of SnO2 thick film. The results were interpreted as a function of the crystallite size. As the crystal lite size reduced, the sensitivity to H-2 gas enhanced at temperatures lower than 300-degrees-C, but at those higher than 350-degrees-C it d id not. The temperatures showing the minimum resistance in air and the maximum sensitivity to H-2 gas decreased with reduction of the crysta llite size. The temperature variations were assigned to the change of the activation energies of the oxygen adsorbates. It is suggested that the decrease of activation energies is one of the reasons for the sen sitivity enhancement with the fine powder.