Improvement in gas sensitivity of ZnO thick film to volatile organic compounds (VOCs) by adding TiO2

A highly sensitive ZnO-TiO2 based thick film volatile organic compound (VOC) sensor had been developed. TiO2 was mixed in ZnO in various weight percentage (0%, 1%, 5% and 10%). The X-ray diffraction (XRD) analysis of mixtures sintered at 650 degreesC for 2 h revealed the appearance of Zn2TiO4 phase, whereas the surface morphological studies of the films based on the mixture indicated that the average grain size increased with the addition of a small amount of TiO2 in ZnO then decreased with higher TiO2 level. It was observed that the sensitivity greatly increased with increasing the content of TiO2. When the sensors operated at operating temperature of 370 degreesC, their sensitivity increased quasi-linearly with the concentration of alcohol and acetone, but the sensitivity to benzene, toluene and xylene increased rapidly in a lower concentration range then slowly in higher concentration range. The sensors showed rapid response-recovery time and the response and recovery time was around 10 and 5 s, respectively, at operating temperature >320 degreesC. (C) 2003 Elsevier B.V. All rights reserved.