A Thick-Film NO2 Sensor Fabricated Using Zn–Sn–Sb–O Composite Material

Abstract

Thick film NO2 sensors comprised of various Zn–Sn–Sb–O composite materials have been studied. The gas-sensing materials were prepared by sintering a mixture of ZnO, SnO2 and Sb2O3 powders at 800, 1000 and 1200°C. Thick films were fabricated on an Al2O3 substrate using a conventional screen-printing method. The atomic ratios of the fabricated films were confirmed by the results obtained from EPMA (Electron probe micro analysis). The dominant compositions of the sintered gas-sensing materials were characterized by XRD (X-ray diffraction). It was found that the composition of the gas-sensing material depended on the initial Sb/Zn atomic ratio, where the gas-sensing material shows almost single-phase ZnSb2O6 when Sb/Zn = 2.0, a mixture of ZnSb2O6 and SnO2 when Sb/Zn = 1.0 and a mixture of SnO2 and an unknown crystal when Sb/Zn = 0.5. The sensing film shows high sensitivity and excellent selectivity for ppm levels of NO2 gas because the film shows no sensitivity for i-C4H10 and CO gases. The capability for NO2 detection in a practical application was examined by using the sensor to monitor the gas which was emitted from a kerosene heater.