Long-lasting stability and low-concentration SO2 gas detection aptitude of Sn-doped alumina sensors

Abstract

The Sn-doping effect on the SO2 gas sensing properties has been investigated by a resistance-based measurement method. During structural analysis, the undoped aluminium oxide (Al2O3) nanoparticles display a rhombohedral phase and the Sn-doped nanoparticles reveal the orthorhombic phase which causes a diffraction shift to a higher angle. From the surface analysis, particles expose dense microstructure, which is further enhanced by doping. High-resolution scanning microscopy images confirm a non-identical orientation of particles, suggesting polycrystalline nature. Besides, the particles are interconnected through one-by-one approach by forming a necklace of bead-like structure. The optical spectroscopy measurement endows a decrease in absorption intensity followed by an increase in bandgap with increasing Sn-doping concentration (SnxAl2-xO3). In sensor investigation, Sn-doped sensor senses the SO2 gas more efficiently even at low and higher concentrations i.e. from 10 to 300 ppm. The sensor adduces an elevated sensitivity of 78.14% at 300 ppm. In addition, the sensor adsorbs the gas molecules within 17 s, depicting a fast response time. As a result of the greater sensitivity, assistive technology such as pre-concentration is no longer required. The Sn-doped sensor bestows 96.83% reproducibility, showing a practical importance.