Natural zeolitic material of the clinoptilolite type and its iodine forms were 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 -25C at different relative humidities (75 to 11%). The conductivity of the iodine forms (10−5S/cm, on average, at 20C 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 I−3 ions) which were removed by heating at 200C. Conductivity measurements, carried out before and after heating at 200C, indicated that the presence of iodine species on the surface of the particles was 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.

AC and DC Conductivity Study of Natural Zeolitic Material of the Clinoptilolite Type and its Iodine Forms. M.Rehakova, A.Sopkova: Solid State Ionics, 1993, 66[1–2], 189–94