Dielectric properties of faujasites: comparison between types X and Y during dehydration

Autor: J. Vanderschueren, A. Abdoulaye, Jean-Victor Zanchetta, Jean-Charles Giuntini, F. Di Renzo, G. Chabanis
Rok vydání: 2000
Předmět:
Zdroj: Microporous and Mesoporous Materials. 34:317-325
ISSN: 1387-1811
DOI: 10.1016/s1387-1811(99)00184-5
Popis: The dielectric properties of two faujasites, X and Y, were studied in a wide range of frequencies (10–106 Hz) at several temperatures and for various outgassing temperatures TT (100–400°C). Conductivity measurements were undertaken with the aim of describing the possible mechanisms of conduction in these materials. The polarization conductivity is ascribed to the cations in the large cages (supercages). The d.c. conductivity is related to the migration of the exchangeable cations over relatively large distances. The corresponding activation energies vary from 0.58 to 0.9 eV for NaX and from 0.61 to 0.85 eV for NaY. These energies vary with TT in a different way for each zeolite. Two relaxation domains, attributed to the cations on sites II and III′, are a function of the dehydration temperature. The activation energies are 0.41–0.58 eV. These two processes are shown by the technique of the thermally stimulated currents–relaxation map analysis.
Databáze: OpenAIRE