Abstract
Changes in the optical absorption and electron paramagnetic resonance (EPR) spectra of manganese-doped SrF2 single crystals under thermal treatments in different atmospheres have been studied. The influence of the presence of water vapour in the annealing atmosphere has also been analysed. No changes were induced by thermal treatments at temperatures below 700 degrees C. By annealing up to 900 degrees C in a dry atmosphere, only a decrease in the Mn2+ cubic signal was observed. Anneals in water-containing atmospheres between 700 and 900 degrees C modify the EPR as well as the optical absorption of the samples. The EPR spectra of two new Mn2+ centres were analysed and values for their spin-Hamiltonian parameters are given. The role played by oxygen and/or hydroxyl impurities, which were incorporated into the bulk after the hydrolysis process, in the structure of these defects is discussed. The results show that Mn2+ modifies the hydrolysis processes in SrF2 under annealing above 700 degrees C in a wet atmosphere and suggest that manganese ions act as a trap for oxygen and hydroxyl impurities.
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