Characteristic of paramagnetic centres in burnt clay and pottery by the EPR method

The samples of natural clay and pottery have been investigated by using electron paramagnetic resonance (EPR) method. Because of young age (100–5000 years old) of these materials and the presence of iron compounds the big doses (1–200 kGy) of irradiation have been used. The authors investigated whole material without quartz extracting from acid washing. In natural clay the EPR lines were observed which disappear after clay burning and they were also not present in EPR spectrum of pottery. After clay burning at temperatures similar to these at which pottery was burnt the spectra of clay became similar to pottery spectra. These EPR spectra have also similar hyperfine structure for which the gg factors are equal g1=2.0595g1=2.0595, g2=2.0079g2=2.0079, and g3=2.0018g3=2.0018 for clay and g1=2.0602g1=2.0602, g2=2.0079g2=2.0079 and g3=2.0019g3=2.0019 for pottery. For these lines the [AlO4]0[AlO4]0 centre in quartz was ascribed.