Abstract: High ionically conducting single-phase NYSsamples have been prepared by both the conventional solid state reaction and the Sol-Gel method.Because of the high sensitivity of phase purity and ionic conductivity of the samples to the composition of starting materials, we carefully controlled the procedure of syntheses in order to exclude impurity phases, i.e.Na₃YSi₃O₉ and Na₉YSi₆₀O₁₃. Ionic conductivity and conducting activation energy of samples prepared by these two methods have been determined by means of ACimpedance technique.From the analysis of their impedance spectra, we know that the sample prepared by conven tional solid state reaction has some what lower ionic conductivity and higher conducting acti vation energy. On the other hand, ionic conductivity of the sample prepared by Sol-Gel method is comparatively higher, and its conducting activation energy is lower.In accordance with the ionic conducting property, the microstructure observed by SEMof these two sam ples shows big difference, that is, the latter has small and uniform grains which connected more closely but the former has large and nonuniform grains packed loosely.Compared with the former, the latter has more conducting paths for the mobile ions, hence higher ionic conductivity.

Key words: Sol-Gel method, NYS, Ionic conductivity, Conducting activation energy