Combined influence of titania and silica precursors on the properties of thin film humidity sensing elements prepared via a sol–gel method

Abstract

The present work deals with the comparative investigations of the combined influence of precursors of TiO2 and SiO2: Tetrabutyl orthotitanate, Tetraethoxysilane and (3-Glycidyloxypropyl)trimethoxysilane in the presence of Ce-ions on the properties of the respective thin film humidity sensing elements prepared via a sol–gel method and sintered at 400°C. SEM, EDX and XRD analyses of the obtained samples have been carried out to study their surface morphology and structural composition. The electrical characteristics and parameters of the samples have been investigated by means of an impedance analyzer. It has been established that the type and proportions of the precursors substantially affect the structure of the films obtained and their humidity sensing properties. The combination of both types of precursors of TiO2 and SiO2 in all cases results in an enhancement of the sensor elements’ response to humidity compared to the use of only one of these precursors. The change in resistance of the samples reaches about four orders of magnitude within the range from 15 to 93% relative humidity at a frequency of 20Hz and at 25°C.