Defect processes involving oxygen-compensated sites in CaF2 precipitates doped with lanthanides and actinides

Oxygen incorporation into calcium fluoride precipitates doped with lanthanides and actinides is investigated by use of the technique of site-selective spectroscopy. Fluorescence from erbium in specific fluoride- and oxygen-compensated sites is monitored as a function of the ignition temperature of the precipitate to study the conversion from fluoride to oxygen compensation. Another process, thermal annealing of a disordered precipitate to give a well-defined lattice, is also followed. Changes in both oxygen compensation formation and lattice annealing are found to occur upon the addition of other trivalent and monovalent ions. The results provide a better understanding of the solid-state chemistry involved in new methods of chemical analysis using rare-earth doped CaF2 precipitates, and how certain interference effects can arise. Also included is a study of the temperature dependence of fluorescent sites in CaF2:U6+