Synthesis, Thermal properties and electrical conductivity of Na-Sialate geopolymer

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Abstract In this work, the central focus is upon the synthesis of new Na-Sialate geopolymer concerning as ionic conductive material for electric and electrochemical devices. The studied material was prepared at ambient temperature by a mixture of metakaolin and sodium hydroxide. In order to study the change in gel structure and phase composition at each heating step. The synthetic compound was characterized by several techniques.The phase identification of Na-Sialate geopolymer, was carried out by powders X-ray diffraction, showed an amorphous character at ambient temperature. As well as minor amounts of high temperature crystalline phases were appeared which were: zeolite (300-600°C), Nepheline (NaAlSiO4) (900-1150° C). Above 1200°C, the structural reorganization occurs due to the phase crystallization of corundum (α-Al2O3). The dissolution of the grains by the liquid phase formed induces the conversion of the structure of the material from sialate [-Si-O-Al-O] to sialate siloxo [-Si-O-Al-O-Si-O-]. These results were confirmed by Fourier transform infrared spectroscopy (FT-IR).The thermal analysis offered a thermal stability of Na-geopolymer up to 1400°C.The electrical measurements were applied to investigate Na+ ions conductivity of Na-geopolymer. The results showed that Na-Sialate geopolymer materials exhibit high ionic conductivity of approximately 5.10−5 S.cm− 1 in air, at room temperature.

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