Abstract
We have studied the optical absorption, luminescence, and electron paramagnetic resonance of EuF3- and EuF2-activated fluorohafnate glasses. The glasses prepared with EuF2 contain both di- and trivalent europium. The fraction of divalent europium clusters in the glass host decreases with decreasing EuF2 concentration. Eu2+ luminescence in the fluorohafnate glasses is quenched, which is due the overlap of Eu2+ excited state levels with the conduction band of the glass, resulting in nonradiative relaxation through Hf3+ levels in the conduction band. The Eu3+ luminescence spectra contain lines corresponding to transitions from several levels of the 5D multiplet to levels of the 7F multiplet. The relationship between transitions from different 5D levels depends on europium concentration and temperature.
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