Probing the Strontiumthiodisilicate Host with Trivalent Cerium (original) (raw)
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Optical Materials, 2010
Divalent europium is notorious for the tunability of its emission, depending on the host material in which it is used as a dopant. In europium-doped alkaline earth thiosilicates, two distinct emission bands can be observed for the alkaline earth metals Mg, Ca and Sr while only a single band is found for barium thiosilicate. In this work, we first complete the data with europium-doped magnesiumthiosilicate. Then, the solid solution of calcium and magnesium thiosilicate is presented. To conclude, the presence of multiple emission peaks in some compounds is explained on a structural basis, by analysing the possibilities for preferential orientation of the europium d-orbitals.
Luminescence of Cesium Thiocyanate (CsSCN) doped with Eu 2+ (CsSCN:Eu 2+ )
Many host lattices have been investigated, as it is known that the effect of the host lattice in luminescence is complex, therefore this work seek to investigate Cesium Thiocyanate (CsSCN) as a suitable host lattice in luminescence. Cesium Thiocyanate is doped with EU 2+ and the Luminescence of the doped compound measured. CsSCN was prepared from Cd(SCN) 2 and Ca(CO) 3 . The prepared CsSCN was then doped with 0.05% EU 2+ at 220 oc . The Luminescence spectra of the CsSCN:EU 2+ was measured using a D5000diffractometer. The emission spectra obtained is broad with the maximum at 19801cm -1 . The spectra obtained were in agreement with typical thiocynante spectra that were doped with EU 2+ . CsSCN can therefore be used as a host lattice with some minor problems of decomposition by products.
A XAS study of the luminescent Eu centers in thiosilicate phosphors
Physical Chemistry Chemical Physics, 2013
Due to its bright yellow-to-red emission, europium doped Ca 2 SiS 4 is a very interesting material for phosphor converted light emitting diodes. The emission spectrum is highly dependent on the Eu concentration and can consist of more than one emission band. We combined X-ray absorption fine structure and photoluminescence measurements to analyze the structure of europium centers in (Ca,Eu) 2 SiS 4 luminescent powders. This paper provides an explanation for the concentration dependency of the emission spectra. We find that at low dopant concentrations a large fraction of trivalent europium ions is unexpectedly present in the powders. These trivalent europium ions tend to form defect clusters in the luminescent powders.
ACS Applied Materials & Interfaces, 2014
A new Ce 3+-activated thiosilicate phosphor, BaLa 2 Si 2 S 8 :Ce 3+ , was synthesized by using solid-state methods in a fused silica ampule and found to crystallize in the structure type of La 2 PbSi 2 S 8. The crystal structure has been characterized by synchrotron X-ray diffraction and refined with Rietveld methods. This novel cyan-emitting phosphor can be excited over a broad range from UV to blue light (380−450 nm) and generates a broadband emission peaking at 471 nm with a quantum efficiency of 36%. Nonradiative transitions between Ce 3+ ions in BaLa 2 Si 2 S 8 :Ce 3+ have also been demonstrated to be attributable to dipole−dipole interactions, and the critical distance was calculated to be 17.41 Å. When BaLa 2 Si 2 S 8 :Ce 3+ phosphor was utilized to incorporate with yellow-emitting (Sr,Ca) 2 SiO 4 :Eu 2+ phosphor and red-emitting CaAlSiN 3 :Eu 2+ phosphor on a 430 nm blue LED chip, a warm white light LED device with color rendering index of ∼96 was obtained. The results indicate that cyan-emitting BaLa 2 Si 2 S 8 :Ce 3+ can serve as a potential phosphor for incorporation in fabrication of solid-state lighting. The preparation, spectroscopic characterization, quantum efficiency, decay lifetime, thermalquenching behavior, and related LED device data are also presented.
Broadband Luminescence in Rare Earth Doped Sr2SiS4: Relating Energy Levels of Ce3+ and Eu2+
Materials, 2013
Sr 2 SiS 4 :Ce 3+ is an efficient blue-emitting (460 nm) phosphor, excitable with light of wavelengths up to 420 nm. From the excitation spectrum, we construct the energy level scheme and use it to check the predictive power of the Dorenbos model, relating the positions of the Ce 3+ energy levels with those of Eu 2+ in the same host. For strontium thiosilicate, this method gives excellent results and allows us to determine which of two available crystallographic sites is occupied by cerium. We use the Dorenbos method for extracting information on the coordination of Ce 3+ from the observed crystal field splitting.
Eu 2+ luminescence in strontium aluminates
Phys. Chem. Chem. Phys., 2015
The luminescence properties of Eu2+ doped strontium aluminates are reported and reviewed for a variety of aluminates, viz. SrAl12O19, SrAl4O7, Sr4Al14O25, SrAl2O4 and Sr3Al2O6.
Journal of Solid State Chemistry, 1999
Recently prepared Ce 3 (SiS 4 ) 2 I exhibits a strong room temperature luminescence in the blue region of the visible spectrum associated to a Ce III -5d 1 PCe III -4f 1 electronic transition. In order to approach the emission mechanisms, the La 3؊x Ce x (SiS 4 ) 2 I family has been investigated by optical techniques at 6 and 300 K. At low temperature luminescence of the two crystallographically distinct cerium cations was evidenced along with an intrinsic luminescence of the lanthanum matrix. The in6uence of the halogenide on the optical properties has been studied through the substitution of iodine by chlorine and bromine which permits us to follow the increase in energy of the 4f+5d gap in the Cl < Br < I series.
The luminescence of europium in strontium borates
Materials Chemistry and Physics, 1993
At 300 K the Et?' ion luminesces efficiently in SrB,O,, and to a lesser extent in SrBsOlo and Sr,B,O,. In the last compound the lowest 4f-5d absorption band is at extremely low energy for Et?'. Due to this and a large Stokes shift, the Et?+ emission band has its maximum at 590 nm. From a comparison with the luminescence of Ce3+ and Pb*' in this lattice it is concluded that a strong non-cubic crystal field splits the 5d excited state, causing the lowest f-d absorption transition to be at a low energy position. In SrB204 and Sr,B,O:, only Eu3+ was found. An explanation for this is proposed on the basis of a charge-compensation mechanism for Eu3+; the luminescence of this ion is discussed as well.