Effects of NiO/TiO_2 addition in ZnFe_2O_4-based gas sensors in the form of polymer thick films

摘要

The aim of this work is to investigate the properties of gas sensors, with active layers that have been prepared by screen-printing. The active layers primarily consist of zinc ferrite (ZnFe_2O_4), which was prepared using iron oxide (Fe_2O_3) and zinc oxide (ZnO) as the raw materials. X-ray diffraction (XRD) was used to confirm the final composition of the powder while SEM was used to examine the grain size. Following this the ZnFe_2O_4 powder was combined with NiO, TiO_2, PVB and carbon black to form a thick film paste and deposited on glass substrates with interdigitated electrodes. The sensor was then interfaced with three resistors to form a bridge circuit. The films were used to detect butanol and pentanol in the concentration range 0-1000 ppm and hexanol from 0-250 ppm. The sensitivity of the devices to gas vapours was calculated as ΔV=(V_(gas)—V_o). The sensitivity increased with increasing gas vapour concentrations. The device showed its highest sensitivity to hexanol followed by pentanol, butanol, propanol, ethanol and finally methanol. The effect of the temperature on the sensitivity of the device to both propanol and toluene has been studied. The effect of adding TiO_2 and NiO to ZnFe_2O_4 on the response and recovery times was also addressed.