Screen-printed MgAl2O4 semi-thick film based highly sensitive and stable capacitive humidity sensor

Abstract

In this paper we have reported on the excellent humidity sensing properties of screen-printed magnesium aluminate (MgAl2O4) porous, semi-thick film, capacitive sensor in the range of 2%–98% RH. MgAl2O4 nanoparticles were prepared by a facile solid-state reaction route. Screen printing technique was employed to prepare the MgAl2O4 porous semi-thick film. The binders used in screen-printing generated pores on the film surface during firing of the film. The as prepared nanoparticles and the thick film were characterized by different sophisticated techniques, viz. X-ray Diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Field Emission Scanning Electron Microscopy (FESEM), Energy Dispersive X-ray (EDX), BET-surface area analysis, laser diffraction-based particle size analysis, and contact angle measurement. Parallel plate capacitive configuration was used whereby the sensor film was interposed between copper bottom and silver top electrodes. The sensor exhibited high and stable response up to 98%RH with a detection lower limit of 2%, which is seldom reported. Further we observed low dissipation (<2), fast response (~66 s) and recovery (~71 s) times, low hysteresis (~109 pF at 89% RH), excellent repeatability (at least 15 cycles), and long-term stability (at least 6 months). This sensor is suitable for commercial applications in tea industry, food packaging, hospitals etc.