Karpova L. Тhermoactivation spectroscopy of Bi12SiO20 crystals doped by Cr and Mn ions.

The object is photorefractive Bi12SiO20 crystals doped by Cr and Mn ions (BSO:Cr, BSO:Mn). The aim of the work is the determination the parameters of electrically active defects and the investigation of the slow polarization processes in BSO:Cr, BSO:Mn crystals . Methods - thermally stimulated polarization (TSP), thermally stimulated depolarization (TSD) and the temperature-frequency dependences of dielectric permitivity. The formtion of thermo- and photoelectret states (TES and FES) has been studied. It is shown, that doping by Cr and Mn ions causes the appearance of new thermally stimulated depolarization (TSD) peaks and increase of TES and FES charges in comparison with undoped Bi12SiO20 crystals.The temperature behavior of TSD peak intensities depending on conditions of preliminary polarization (the polarization temperature and the polarization voltage) has been obtained in cases when the order of the relaxation kinetics exceeds unity. The space charge and the dipole polarization mechanisms have been identified for each TSD peak. Considerable influence of association dissociation processes of electrically active defects on the formation of the TES has been established in BSO:Cr, BSO:Mn crystals. The temperature-frequency dependences of dielectric permitivity in BSO:Cr, BSO:Mn crystals with the thermoelectret state have been investigated. The obtained results about the parameters of electrically active defects in BSO:Cr, BSO:Mn crystals is recommended to be used for optimization of operation of writers and treating of the optical information.