Irradiation induced defects in glasses resulting in the photoionization of polyvalent dopants

The extent of solarization is strongly influenced by many factors such as glass matrix, dopants, or irradiation source. Typical irradiation induced effects are illustrated in a series of glasses doped with a selection of polyvalent ions. Intrinsic and extrinsic defects, consisting of electron and hole centers, are characterized with optical and EPR spectroscopy. Used in combination, both spectroscopic methods allow to detect a wide range of defects. UV-lamp irradiation causes in fluoride-phosphate glasses the photoreduction of Ni2+, Pb2+ and Ag+ while Co2+, Ce3+, Fe2+ and Mn2+ are photooxidized. The influence of the glass matrix is evident for Ni2+ which is photooxidized in borosilicate, but reduced in fluoride-phosphate glasses. Iron ions also show different redox reactions depending on the glass matrix, as well as on the melting conditions, which will be shown for low alkaline borosilicate glasses doped with iron or tin. Changes in the nature and the rate of defect formation could be observed within the irradiation process of a fluoride-phosphate glass co-doped with Mn2+ and Fe2+ and during thermal annealing of a lamp irradiated phosphate glass containing Co2+. The series Mn2+, Fe2+, Co2+ and Ni2+ shows a trend of increased photooxidation with increasing electro-negativity or decreasing mass of the ions. (C) 2003 Elsevier B.V. All rights reserved.