Hydrogen sensing properties of SnO 2 varistors loaded with SiO 2 by surface chemical modification with diethoxydimethylsilane

Abstract

Effects of chemical surface modification with diethoxydimethylsilane (DEMS) on the H 2 sensing properties of pure SnO 2 and Pd/SnO 2 as a varistor-type sensor have been investigated. The DEMS treatment resulted in an increase in the breakdown voltage, especially in air, and in an improvement in H 2 sensitivity for both SnO 2 and Pd/SnO 2 varistors. A.C. impedance measurement has revealed that variations in potential barrier height per grain boundary, V gb, with H 2 concentration are well coincident with the breakdown voltage shift induced by the presence of H 2. Thus, it was confirmed that the improved H 2 sensitivity arose from the increased V gb in air induced by the SiO 2 thin film coating by the DEMS treatment. The limitation of neck growth between SnO 2 particles by the SiO 2 thin film coating is anticipated to be responsible for the increased V gb.