ZnO nanostructured coatings have been prepared on Al 2 O 3 substrates fitted with Au electrodes on one side and a Pt heater on the other, forming a solid-state gas sensor. The coatings were deposited by solution precursor plasma spraying (SPPS) using aqueous zinc acetate as the precursor solution. FE-SEM images show that the coatings are nanostructured with grain sizes of 50-100 nm. Surface morphology and grain size were found to be influenced by the flow rate of H 2 in the plasma forming gas. The gas sensing function was characterized by measuring the electrical resistance of the coating in the presence of NO 2 gas, showing good sensitivity down to the sub-ppm range.

This work studied the possibility of using a sensor based on plasma-sprayed zinc oxide (ZnO) sensitive layer for NO 2 detection. The atmospheric plasma spray process was employed to deposit ZnO gas sensing layer and the obtained coating structure was characterized by scanning electron microscopy and X-ray diffraction analysis. The influences of gas concentration, working temperature, water vapor in testing air on NO 2 sensing performance of the ZnO sensors were studied. ZnO sensors showed a good sensitivity and selectivity to NO 2 at an optimal working temperature.