Improvement in gas sensitivity of ZnO thick film to volatile organic compounds (VOCs) by adding TiO_2

摘要

A highly sensitive ZnO-TiO_2 based thick film volatile organic compound (VOC) sensor had been developed. TiO_2 was mixed in ZnO in various weight percentage (0 percent, 1 percent, 5 percent and 10 percent). The X-ray diffraction (XRD) analysis of mixtures sintered at 650 deg C for 2 h revealed the appearance of Zn_2TiO_4 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 TiO_2 in ZnO then decreased with higher TiO_2 level. It was observed that the sensitivity greatly increased with increasing the content of TiO_2. When the sensors operated at operating temperature of 370 deg C, 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 deg C.