Effects of tetraethyl orthosilicate binder on the characteristics of AN SnO 2 ceramic-type semiconductor gas sensor

Abstract

As part of the research to improve the long-term stability of sintered SnO 2 semiconductor gas sensors, we examined the effect of the degree of polymerization (referred to as DP) of ethyl silicate binders added to the sensors on their characteristics. DPs in the range one to four were investigated. By using a binder with a large DP gas sensibility is increased and the sensor resistance is decreased. Humidity dependency and long-term stability are improved by using a binder with a smaller DP. A binder whose DP is more than 2.0 is needed in order to obtain the necessary mechanical strength of the sensor. We concluded that the binder's DP should be 2.5 for the sensor to be stable during long-term operation. Through measurements of H 2 oxidation activity and temperature-programmed desorption for H 2O and O 2, we concluded that the long-term change in the sensor sensitivity is based on the change in its catalytic activity caused by the increase or decrease of the amount of the hydroxyls on its surface.