Assignment of dielectric loss of K–L zeolite

Abstract

Dielectric spectra of zeolite L (LTL) with potassium ions were measured to investigate movements of potassium ion in it. K,TMA–L was prepared through an ion-exchange of K₉–L with tetramethylammonium (TMA) ion, and changed to K,H–L by gentle calcination in air. Since the TMA ion in K,TMA–L was expected to exclusively occupy site D, the hydrogen ion in K,H–L was considered to be located around site D. K_9−xH_x–L with 0 ≤ x ≤ 1.1 showed an apparent single loss peak, and the magnitude of loss peak decreased with increasing x. Based on the variation of magnitude of loss peak with x, the loss was attributed to movements of K⁺/D. The apparent single peak contained two loss peaks. The reason why the movements of K⁺/D brought about two losses was due to jumps among three inequivalent sites containing the site D. The activation energy of movement related to the main loss decreased with an increase in x. The decrease in activation energy was explained by the influence of cation–cation repulsion, namely, the repulsion energy between K⁺/D and cation/neighbor-D decreases after the replacement of K⁺/neighbor-D with a hydrogen ion because of the increase in distance between cations, and hence the activation energy of movement of K⁺/D decreases.