Microstructure and gas sensing properties of solution precursor plasma-sprayed zinc oxide coatings

ZnO nanostructured coatings have been prepared on Al2O3 substrates fitted with interdigitated Au electrodes on one side and a Pt heater on the other side, and explored as a gas sensor. The coatings were deposited by solution precursor plasma spray (SPPS) using zinc acetate Zn(CH3COO)(2) aqueous solution as solution precursor. The SPPS process has proven its simplicity and reliability in fabricating polycrystalline ZnO coatings as verified by XRD structural analysis. The FE-SEM images confirmed that the coatings are nanostructured with grain size ranging from 50 to 100 nm. The surface morphology and coating grain size is influenced by the H-2 gas flow rate in plasma forming gas. The properties of the sensors based on the SPPS ZnO coatings towards NO2 as well as other hazardous gases were characterized and the sensors showed good sensitivity to NO2 gas in sub-ppm range. The influence of gas humidity on sensor responses was also studied. (C) 2014 Elsevier Ltd. All rights reserved.