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Autori: M. Stef, A. Pruna, N. Pecingina-Garjoaba, I. Nicoara
Editorial: Acta Physica Polonica A, 112, p.1013-1018, 2007.
Calcium fluoride crystals doped with YbF3 and co-doped with LiF and NaF were grown using the vertical Bridgman method. Several of rare-earth ions (such as Eu, Sm, Ho, Tm, and Yb) can be stabilized in the divalent state in the CaF2. The change of valence was attained by various methods. The optical absorption spectra reveal the characteristic absorption bands of
the Yb3+ and Yb2+ ions. This means that the developed crystal growth process achieves a good Yb3+ to Yb2+ conversion in the as-grown crystals. The influence of other impurities, such as Na+ or Li+, on the absorption and emission spectrum of YbF3-doped CaF2 was studied. The Li+ and Na+ ions drastically decrease the absorption coe±cient of the Yb2+ ions in the UV band and the emission intensity by excitation in 230 nm.
Cuvinte cheie: Defecte, impuritiati, compusi de calciu, proprietati optice // Defects, impurities, calcium compounds, optical properties