Different Eu-centres in CaS:Eu, Cl

Danilkin, M. I.; Must, M.; Pedak, E.; Pärnoja, E.; Ryasnyi, G. K.; Shpinkov, I.N.; Shpinkova, L.G.; Seeman, V.

doi:10.1016/1350-4487(95)00277-l

Cited by 6 publications

(5 citation statements)

References 8 publications

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“…Just a small excess of fluoride anions has an oxidizing effect on europium, while a significant excess of fluorine conversely has a reducing effect. A similar effect of halogens on europium was observed earlier in calcium sulfide [14]. This feature makes it possible to control the charge state of europium in CaF 2 .…”

supporting

confidence: 71%

Formation of Eu2+ and Eu3+ centers in synthesis of CaF2:Eu luminophores

et al. 2007

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UDC 546.161;535.37:(538.958+538.955) We have studied the effect of CaF 2 :Eu luminophore synthesis methods on the charge state of europium. We have shown that Eu 3+ predominates over Eu 2+ in samples obtained by coprecipitation of europium with calcium fluoride, and the ratio Eu 3+ /Eu 2+ grows as the total amount of europium increases. Partial charge conversion of the europium occurs during calcination of the samples, due to changes in the excess fluorine balance. We studied the luminescence, magnetic susceptibility, and EPR of the synthesized samples. We have shown that in a solid solution, europium forms large ordered clusters, determining both the luminescent and the magnetic properties of the material.

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supporting

confidence: 71%

Formation of Eu2+ and Eu3+ centers in synthesis of CaF2:Eu luminophores

et al. 2007

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“…For CaS:Eu luminophors, Danilkin et al [136] observed only one Mössbauer absorption peak, corresponding to Eu

^{3 +}

ions. Pham-Thi et al [103] synthesized CaS:Eu using the flux method with Na and K. The Mössbauer spectrum of the sample prepared with Na polysulphide flux showed only Eu

^{3 +}

absorption while with K flux both ions were detected.…”

Section: Materials Overviewmentioning

confidence: 99%

Characterization of Luminescent Materials with 151Eu Mössbauer Spectroscopy

Steudel

Johnson

et al. 2018

Materials

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The application of Mössbauer spectroscopy to luminescent materials is described. Many solids doped with europium are luminescent, i.e., when irradiated with light they emit light of a longer wavelength. These materials therefore have practical applications in tuning the light output of devices like light emitting diodes. The optical properties are very different for the two possible valence states Eu2+ and Eu3+, the former producing ultraviolet/visible light that shifts from violet to red depending on the host and the latter red light, so it is important to have a knowledge of their behavior in a sample environment. Photoluminescence spectra cannot give a quantitative analysis of Eu2+ and Eu3+ ions. Mössbauer spectroscopy, however, is more powerful and gives a separate spectrum for each oxidation state enabling the relative amount present to be estimated. The oxidation state can be identified from its isomer shift which is between −12 and −15 mm/s for Eu2+ compared to around 0 mm/s for Eu3+. Furthermore, within each oxidation state, there are changes depending on the ligands attached to the europium: the shift is more positive for increased covalency of the bonding ligand X, or Eu concentration, and decreases for increasing Eu–X bond length.

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“…For the synthesis of CaS-based luminophors, high purity grade calcium sulfide was obtained by the reduction of CaSO 4 using purified hydrogen flowing at 1150-1170 K. 19 The product contained up to 99.4% (m/m) of the theoretical quantity of sulfide anions. Then, the required amounts of dopants (Eu 2 O 3 for Eu, Sm 2 O 3 for Sm and anhydrous CaCl 2 for Cl) were added to the CaS.…”

Section: Analysis Of Eu-and Sm-doped Cathodoluminophorsmentioning

confidence: 99%

“…The samples were heated with 2-10% of sulfur under flowing argon at 1370-1420 K for 30 to 45 min. 19 The halogens are widely used as a flux in the preparation of CaS: Eu, Sm luminophors. Moreover, the effect of added Cl on the cathodoluminescence efficiency of CaS: Eu was pointed out by Lehmann and Ryan.…”

Section: Analysis Of Eu-and Sm-doped Cathodoluminophorsmentioning

confidence: 99%

“…In earlier reports, we studied the synthesis of CaS: Eu, Cl luminophors, electron paramagnetic resonance (EPR), Mo ¨esssbauer effect and luminescence properties of cathodoluminophors. [18][19][20] There are many publications on the synthesis and physical properties of luminophors, but few reports on spectrochemical analysis of luminescence materials have been found. The aim of this study is to develop a spectrochemical method for the analysis of different luminophors, such as CaS: Eu, Cl, CaS: Eu, Sm, and the determination of europium and samarium dopants by ICP-AES.…”

Section: Introductionmentioning

confidence: 99%

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