AC AND DC CONDUCTIVITY STUDY OF NATURAL ZEOLITIC MATERIAL OF THE CLINOPTILOLITE TYPE AND ITS IODINE FORMS

Natural zeolitic material of the clinoptilolite type and its iodine forms have been investigated by X-ray powder diffractometry, IR, X-ray photoelectron spectroscopy, thermal analysis and ac-dc conductivity as well as by EMF measurements. The ac conductivity of the natural zeolitic material was measured in the temperature range from 20 to -25-degrees-C at different relative humidities (75 to 11%). The conductivity of the iodine forms (10(-5) S cm-1, on average, at 20-degrees-C and 53% RH) was one order of magnitude higher than that of the natural zeolitic material, and turned out to be dependent on the iodine content. XPS measurements showed that the iodine forms contain iodine ions and other iodine species (I2 and/or I3- ions) which are removed by heating at 200-degrees-C. Conductivity measurements, carried out before and after heating at 200-degrees-C, indicated that the presence of iodine species on the surface of the particles is probably responsible for the higher conductivity of the iodine forms. The electronic conductivity of the iodine forms, as well as that of the natural zeolitic material, was found to be negligible in comparison with ionic conductivity.