Dielectric spectra of Li⁺ (Na⁺) codoped CaF₂:YbF₃ crystals

Abstract

Calcium fluoride crystals doped with YbF3 and codoped with NaF, LiF were grown using the vertical Bridgman method. The effect of Na+ and Li+ ions on the optical and dielectric spectra was studied. The relaxation parameters (the activation energy for dipole reorientation and relaxation time constant) and the number of the dipoles, ND, that contribute to the dielectric relaxation have been determined from the dielectric spectra. The correlation between ND and the optical spectra is also discussed. A comparison of our results with those obtained by other authors is also given. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Growth and Characterization of Doped CaF2 Crystals

“…In order to obtain high Yb 3+ -Yb 2+ conversion in the as grown crystals, we have developed a special growth procedure. Rare-earth ions -doped and PbF 2 -codoped CaF 2 crystals were grown using vertical Bridgman method [Nicoara et al, 2006a[Nicoara et al, , 2006b[Nicoara et al, , 2008a[Nicoara et al, , 2008b[Nicoara et al, , 2008cPruna et al,2009;Paraschiva, 2010]. As starting materials suprapure grade calcium fluoride, YbF 3 , ErF 3 and PbF 2 have been used.…”

“…The impurity-defects in CaF 2 crystals doped with various ions-Er 3+ , Yb 3+ , Pb 2+ and Na +were studied using the dielectric relaxation method [Nicoara et al, 2006;Nicoara et al, 2006b;Nicoara et al, 2008;Pruna et al, 2009]. Capacitance (C) and dielectric loss (D=tan ) measurements were performed on the samples using a RLC Meter type ZM2355, NF Corporation, Japan over the temperature range of 150-320 K at seven audio-frequencies.…”

“…Six NaF co-doped YbF 3 :CaF 2 crystals with different Na:Yb ratios of 2, 4, 16, 28, 36 have been also grown. Room temperature absorption spectra and dielectric spectra were measured to study the effect of Na + ions on the charge compensating defects formation [Pruna et al, 2009]. Fig.…”