Low temperature synthesis and NO x sensing properties of nanostructured Al-doped ZnO

Abstract

Although ZnO is studied intensively as a sensing material, there are limited reports available on aluminum-doped ZnO (AZO) as a NO x sensor. This paper reports selective NO x sensing characteristics of Al-doped ZnO synthesized in the form of porous pellets sintered at 350 °C. The salient feature of our experimental results is that our sensor can detect small concentrations of NO x at lower operating temperature. It is also observed that as compared to gases such as SO x , HCl, LPG, H 2S, H 2, ammonia, alcohol and acetone it selectively detects NO x due to Al-doping. The amount of Al in ZnO during synthesis is varied between 1 and 10 wt%. Our sensor senses NO x concentration as low as 20 ppm at 100 °C with a %response of 11 and a %response of 740 at 300 °C for 1 wt% Al. Of all the compositions with Al-doping, 1 wt% is found to give best results. Sensing experiments carried out at 350 °C, however, do not show any significant improvement in the gas sensing properties. The phase contents and lattice parameters were determined by XRD and the average particle size was obtained using Scherrer formula. A probable mechanism for sensing NO x involving oxygen ion adsorption and desorption on the surface of sensor has been suggested.