Dependence of the properties of Nasicons on their composition and processing

Abstract A series of Hong and von Alpen Nasicons has been synthesized by both conventional ball milling and gel processing techniques, and their ionic conductivity, microstructure and stability towards water have been studied as a function of composition and processing. The measured bulk ionic conductivity and activation energy values were found to be dependent on the composition and processing parameters. A glass phase (which is basically a sodium silicophosphate with some dissolved zirconia) exists in all compositions irrespective of the processing method. The glass phase has a high ionic conductivity and is rapidly degraded in water. All Nasicons react with water to some degree and this reactivity increases with the increase in the SiO2 content (x value) of the material. Contamination of the materials by alumina during ball-milling increases the reactivity towards water by approximately four decades.