Dielectric properties of an NaX zeolite as a function of the hydration state

The dielectric properties of the NaX zeolite (Si/Al = 1.3) have been measured after different thermal treatments in the temperature range 100-400 degrees C. The frequency domain was varied from 10 to 10(6) Hz, the measuring temperature being in the range 80-150 degrees C. Independent of the outgassing temperature (i.e. the number of water molecules), the ac conductivity is ascribed to migration of the supercage cations. The variation in the migration energy (E-dc) as a function of the adsorbed water molecules (0.9-0.58 eV) shows their influence on the conduction process. Two relaxation domains are observed: 'low-frequency' and 'high frequency' relaxations, which are due to local hops of cations located in sites II and III, respectively. These two relaxations are confirmed by thermally stimulated current measurements. The energies associated with these relaxations vary with the outgassing temperature.