Study of Na+ ions influence on the charge compensating defects in CaF2: YbF3 crystals using dielectric relaxation (original) (raw)
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Dielectric relaxation in ytterbium- and lead-doped calcium fluoride crystals
The European Physical Journal B, 2013
YbF3-doped and 1 mol% PbF2 co-doped CaF2 crystals were grown by vertical Bridgman method using a shaped graphite furnace in vacuum. Dielectric spectra and optical absorption spectra were measured in order to study the influence of Pb 2+ ions on the charge compensating defects formation. The influence of Pb 2+ ions on the various charge compensating defects depend on the YbF3 concentration. For low YbF3 concentrations the influence is stronger than for concentrations higher than 1 mol% YbF3. Dielectric relaxation in double doped (Yb,Pb):CaF2 crystals in order the study the charge compensating defects formation was not reported before.
Influence of Various Impurities on the Optical Properties of YbF3-Doped CaF2 Crystals
Acta Physica Polonica A, 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 Yb 3+ and Yb 2+ ions. This means that the developed crystal growth process achieves a good Yb 3+ to Yb 2+ conversion in the as-grown crystals. The influence of other impurities, such as Na + or Li + , on the absorption and emission spectrum of YbF 3 -doped CaF 2 was studied. The Li + and Na + ions drastically decrease the absorption coefficient of the Yb 2+ ions in the UV band and the emission intensity by excitation in 230 nm.
Growth of YbF 3-doped CaF 2 crystals and characterization of Yb 3+/Yb 2+ conversion
Journal of Crystal Growth, 2008
Calcium fluoride crystals doped with YbF 3 and PbF 2 -, NaF-and LiF-codoped were grown using the vertical Bridgman method. Transparent, high quality, with various high Yb 2+ contents in the as-grown crystals has been obtained using a special procedure. The optical absorption spectra reveal the characteristic ultraviolet (UV) absorption bands of the divalent Yb ions. Influence of the codoping with Pb 2+ , Li + and Na + ions on the absorption spectra and on the Yb 2+ ions content has been studied. High-intensity emission bands in the near-UV spectral region, not reported before, have been observed for excitation by 230 nm. A comparison of our results with those obtained by other authors is also given. r
Optical spectroscopy of Yb2+ ions in YbF3-doped CaF2 crystals
Journal of Crystal Growth, 2008
Transparent colorless Ca 1Àx Yb x F 2+x (x ¼ 0.0007-0.016) crystals were grown using the vertical Bridgman technique. In order to obtain efficient Yb 3+ -Yb 2+ conversion in the as-grown crystals, a special procedure has been developed. Room temperature optical absorption spectra reveal the characteristic UV absorption bands of the Yb 2+ ions in the as-grown crystals, with intensities more than 10 times higher than those reported by other authors using various conversion procedures. The influence of YbF 3 content and of codoping with Pb 2+ ions on the absorption and emission spectra has been studied. Room temperature emission bands in the near UV (not reported before) and in the visible spectral domain have been observed. The emission intensity depends on the dopant concentration. A comparison of our results with those obtained by other authors is also given. r
Concentration distribution of Yb2+ and Yb3+ ions in YbF3:CaF2 crystals
Journal of Crystal Growth, 2008
Calcium fluoride crystals doped with YbF 3 were grown using the Bridgman technique. The optical absorption spectra reveal the characteristic UV-absorption bands of divalent Ytterbium. The absorption coefficient of divalent Yb is more than ten times higher than that of trivalent Ytterbium. This shows that the developed crystal growth process achieves a good Yb 3+ -Yb 2+ conversion. The concentration distribution of the Yb 2+ and Yb 3+ ions among two of the samples was investigated using the optical absorption method. Taking into account the relationship between the optical absorption coefficient and the concentration of the impurities in the sample, the segregation coefficient of the two types of ytterbium ions has been calculated. From our calculations, we obtained the results that the segregation coefficient of the Yb 3+ ions in a CaF 2 host is E1, and for Yb 2+ ions is ol. r
Influence of some impurities on the emission properties of CaF2:YbF3 crystals
2015
Various concentrations of YbF3-doped and NaF or PbF2 co-doped CaF2 crystals were grown using the conventional Bridgman method. Transparent colorless crystals were obtained in graphite crucible in vacuum using a shaped graphite furnace. The crystals have been cooled to room temperature using an established procedure. Room temperature absorption spectra have been obtained using a Shimadzu 1650PC spectrophotometer. Photoluminescent properties in IR spectral range were analyzed using a spectrofluorimeter Horiba Fluorolog 3. An IR laser diode at 932 nm was also used an directly injected in the equipment. The emission spectra are influenced by the concentration of co-dopant added to the melt, and the excitation wavelength. The high emission peak at 979 nm overlaps with the absorption peak. The highest intensity in the IR emission (around 1029 nm) is obtained for CaF2:0.72 mol% YbF3 crystal by excitation at 932 nm (diode lamp).
Distribution of Pb2+ Ions in PbF2-Doped CaF2 Crystals
… Physica Polonica A, 2010
Calcium fluoride crystals doped with various concentrations of PbF 2 have been grown using the Bridgman technique. The optical absorption spectra reveal the characteristic UV absorption bands of the Pb 2+ ions. The distribution of the Pb 2+ -ions along four crystals has been investigated using the optical absorption method. Taking into account the relationship between the optical absorption coefficient and the concentration of the impurities in the samples, the effective segregation coefficient of the Pb 2+ ions has been calculated. Our study shows that the effective segregation coefficient of the Pb 2+ ions in CaF 2 host depends on the dopant concentration, and varies between 0.85 and 1.15, for 0.5 mol%PbF 2 and 3 mol%PbF 2 -doped CaF 2 , respectively.
Journal of Solid State Chemistry, 1980
Experimental measurements of thermal depolarization in crystals of CaF,, grown from the melt containing LiF, NaF, KF, or RbF, reveal a common relaxation (designated M2) with an activation energy of 0.51 eV. In addition, the Li+-and K+-doped crystals exhibit a relaxation (Ml) with an activation energy of 0.34 eV. A similar relaxation has been found in CaF,: Rb+ by J. Fontanella private communication) and in CaF,: Na+ by R. D. Shelley and G. R. Miller (J. Solid Stare Chem., 1, 218, 1970). Theoretical calculations onM+-doped CaF, (where M = Li,Na,K,Rb) are in agreement with the hypothesis that the M2 relaxation is due to Na+ in all four systems studied and is associated with the jump of a nearest-neighbor (nn) anion vacancy (F,-) around the substitutional Na+ ion (Na,+). The assignment ofM1 is less certain, but it appears to be associated with similar L&+-F,-dipoles resulting from Lit impurity present because of the lower volatility of LiF compared to that of KF and RbF. When LiF dissolves in CaF, the Li+ ion also forms quadrupoles consisting of a cation vacancy and two Li+ interstitials and the reorientation of these quadrupoles has also been studied theoretically.