Rice husk ash as a new humidity sensing material and its aging behavior

摘要

Rice husk ash (RHA), a by-product of a biomass combustion plant, was investigated as a new humidity sensing material. The raw material was first calcined at 500 °C for 3 h and then characterized by X-ray diffraction (XRD), N_2 adsorption, laser granulometry and field emission-scanning electron microscopy (FE-SEM). Thick-film sensors were fabricated by screen-printing technique onto α-alumina substrates with Pt interdigitated electrodes and fired at 600 °C. The sensors were characterized by X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FT-IR) and Raman spectroscopy as well as through FE-SEM observations. Furthermore, they were tested towards humidity at room temperature and interferences with some gases such as NH_3 (50 ppm), CO_2 (50 ppm), CH_4 (50 ppm), O_3 (0.5 ppm) and N_2O (15 ppm) were studied too. Unfortunately, though very promising, these sensors exhibited a rather fast aging due to a decrease of the sensing performances after 6 months from the fabrication. FT-IR and Raman spectroscopy, as well as XPS, were then used to understand the degradation phenomena involved in this process.