Investigation of the dielectric relaxation and the transport properties ofporous silicates containing humidity

The dielectric relaxation responses of pelite, which is a porous silicate s ediment containing a low content of inherent humidity, were identified and characterized by employing the experimental scheme of the thermally stimula ted depolarization current (TSDC) spectroscopy. Comparative experiments wer e performed on dry samples. The elementary responses that compose the diele ctric spectrum were recorded by applying certain sampling techniques. The d ielectric relaxation spectrum consists of two low-temperature mechanisms, w hich are related to different modes of relaxation of water molecules. A thi rd one is probably produced by permanent dipoles consisting of point defect s in the calcium participant. Three relaxation mechanisms were sampled with in the intermediate temperature region and were strongly affected by the ou tgassing of the pore network. They correspond to polarization processes occ urring in the multi-layer shell of humidity over the surface the solid aggr egates. At higher temperatures, two mechanisms were traced: the first is re lated to the homogeneous polarization of the specimen as charge carriers mi grate within conducting territories until they are trapped at internal boun daries and the latter is described as a long-distance conduction mechanism which is enhanced by the presence of humidity. The activation energy profil es of the above-mentioned relaxation mechanisms were obtained from the anal ysis of the experimental signals of the thermal sampling and the partial he ating schemes.