Novel Sol-Gel Process to Synthesize NASICON for the Preparation of CO₂ Sensor

Abstract

Solid electrolyte material of NASICON (sodium super ionic conductor) was synthesized through a modified sol-gel process. With the complex effect of oxalic acid added in synthesis, the stability of NASICON precursor solution was apparently improved and the crystallized NASICON phase was successfully achieved at the sintering temperature of 900°C. X-ray diffraction (XRD), Field-Emission Scanning Electronic Microscope (FE-SEM) and impedance spectrum (IS) were utilized to characterize the synthesized material. Making use of its favorite ion conductivity, a NASICON pellet type CO₂ sensor was prepared. The experiments indicated that the sintering temperature has an important influence on its sensing property. With a suitable choice of the sintering condition for the NASICON pellet, a linear relationship of the output electromotive force (EMF) with the target gas concentration for the resulted CO₂ sensor was well demonstrated in the volume gas concentration range of 0.01%-1%. The typical sensitivity is about 65 mV corresponding to a decade change of gas concentration, and the response and recovery time corresponding to 90% output EMF change is 15 s and 28 s, respectively.