The electrical conductivity of compressed powders of an isostructural series of zeolites with the MFI topology was measured using AC impedance spectroscopy. Silicalite-1 and ZSM-5 having various Si/Al ratios and numbers of Na+ and/or H+ were studied at 100% relative humidity or immersed in water (table 46). In the latter case, the conductivity was 1 to 2 orders of magnitude larger than that in saturated water vapour. In water, and at 100% relative humidity, the dependence of conductivity upon the cation content exhibited a maximum. A decrease in conductivity at a high concentration of charge carriers was attributed to an increase in the repulsive interaction between ions in a conductive water layer on the zeolite channel walls.

Water-Assisted Ionic Conductance of Zeolites with ZSM-5 Structure. S.D.Mikhailenko, S.Kaliaguine, E.Ghali: Microporous Materials, 1997, 11[1-2], 37-44

Table 46

Activation Energies for Ionic Conduction in Zeolites