EPR study of radiation-induced defects in the thermoluminescence dating medium zircon (ZrSiO4)

Mineral zircon has been considered as a possible medium for luminescence dating. The development of a suitable material for luminescence dating requires detailed knowledge of the processes taking place during, for example, exposure to ionizing radiation, long-term storage, annealing at moderate temperatures, excitation with (visible–UV) light. In this paper we have described our efforts to obtain relevant dating information by investigating the electron paramagnetic resonance (EPR) spectra of a variety of paramagnetic defects in mineral zircon (ZrSiO4) crystals as a function of the irradiation dose, annealing time and the temperature. The rare-earth ions Dy3+ and Tb3+, which play a crucial role as hole traps and recombination centres, have been investigated in detail and the behaviour of the intensity of the EPR spectra associated with these impurities can be understood in terms of a theoretical model describing the luminescence related processes in zircon. In addition, a number of defects, which can be characterized by SiOmn− have been identified and investigated. Also the behaviour of some of these centres has been analysed in the framework of the theoretical model.