ON THE INTERACTION OF PARAMAGNETIC POINT-DEFECTS IN HEAVY-METAL FLUORIDE GLASSES

The origin and nature of ESR signals of fluoride glasses (ZBLAN: ZrF4/ BaF2/LaF3/AlF3/NaF) doped both with Fe3+ and Fe2+ ions was studied usi ng the temperature and microwave power (P-MW) dependencies as well as a complete simulation of the X-band ESR spectra. For the first time, e vidence is given for the existence of {Fe-II-OH-Fe-III} units (S' = 9/ 2) formed in the glasses involving traces of O-2 and H2O present in th e samples. Fluoride glassy matrices constrain the formation of interac ting species and therefore nonuniform spatial distributions of the dop ants. Reasons are seen (i) in the local structural chemistry (geometri cal and charge compensation reasons), and (ii) in the melting and post -melting processes.