Journal of the Clay Science Society of Japan (in Japanese)

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In this study, NH₄^＋ ion exchange of Na-taeniolite (NaMg₂LiSi₄O₁₀F₂) powders, heat treatment of the ion exchangers and ionic conductivity of the heat-treated ion exchangers (protonated-taeniolites) were investigated. Coarse Na-taeniolite powder was prepared by grounding Na-taeniolite crystal lump obtained by melting method, and fine Na-taeniolite powders were prepared by ball milling or planetary ball milling the coarse Na-taeniolite powder. Na^＋ ions in the interlayer of these Na-taeniolite powders were exchanged with NH₄^＋ ions in NH₄Cl solution at 90°C. The NH₄^＋ ion exchange ratio was improved by ball milling and planetary ball milling, and the planetary ball milled Na-taeniolite, which had the largest specific surface area in this study, showed the highest NH₄^＋ ion exchange ratio (95.9%). Almost NH₄^＋ ions in the interlayer of the ion exchangers were decomposed into protons by heating at 700°C, and the generated protons combined with apical oxygens that have a larger effective negative charge than basal oxygens. Ionic conductivities of protonated-taeniolites were measured at 400 to 600°C by an alternating current four-probe method. The protonated-taeniolite prepared from the planetary ball milled Na-taeniolite, which had a larger amount of proton, showed the highest ionic conductivity of 7.97×10⁻⁵ S/cm.

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