LI Weican, ZHAN Guanghui
(School of Materials Science and Engineering, Hainan University, Haikou 570228, Hainan, China)

Abstract: Currently, tin dioxide (SnO₂)-based ammonia (NH₃) gas sensors face several challenges in practical applications, including high operating temperatures, poor humidity resistance and long response/recovery times. To address these issues, a one-step hydrothermal method was employed to in-situ synthesize La-doped SnO₂ nanomaterials on substrates with interdigital electrodes. Optimally, the 4 wt.% La-doped SnO₂ (LSO-4) demonstrated the highest gas sensing performance. In a high humidity environment at room temperature, the LSO-4 sample exhibited a response value of 33.8% to 20.85 μg·L⁻¹ (30 ppb) NH₃, which is 2.5 times higher than that of pure SnO₂, with a detection limit of 2.363 μg·L⁻¹ and response/recovery times of 2.5 s/6.6 s. The incorporation of La altered the microstructure and electronic properties of SnO₂, resulting in a larger specific surface area, increased pore size and more oxygen vacancy. These changes facilitated the adsorption of O₂ and NH₃ molecules on the surface and the subsequent gas sensing reactions, thereby enhancing the gas sensing performance of SnO₂ for NH₃ detection.
Key words: gas sensor; ammonia detection; tin dioxide; lanthanum doping