Thermal transformation and ionic conductivity of ammonium ion-exchanger prepared from Na-4-mica

Ammonium ion exchange of Na-4-mica and thermal transformation of the ion-exchanger were investigated and the conductivities of the heated ion-exchangers were estimated. More than 95.4% of Na+ ions in the interlayer of the Na-4-mica could be substituted by NH4+ ions after repeating ion exchange four times. Almost of NH4+ ions remained in the interlayer at 700 °C and they were completely decomposed into protons at 900 °C. The conductivities of the ion-exchangers heated at 700–900 °C were 10−7–10−6 S/cm at 700 °C. The conduction mechanism of the ion-exchangers heated at 700 and 800 °C was NH4+ ion migration in the interlayer and that of the ion-exchanger heated at 900 °C was proton migration. However, the contribution of residual Na+ ions to the conduction cannot be excluded.