Europium doped thiosilicate phosphors of the alkaline earth metals Mg, Ca, Sr and Ba: Structure and luminescence (original) (raw)
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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.
Journal of Radiation Research and Applied Sciences, 2015
Europium doped di-strontium magnesium di-silicate phosphor namely (Sr 2 MgSi 2 O 7 :Eu 3þ) was prepared by the traditional high temperature solid state reaction method. The phase structure of sintered phosphor was akermanite type structure which belongs to the tetragonal crystallography with space group P42 1 m, this structure is a member of the melilite group and forms a layered compound. The EDX and FTIR spectra confirm the present elements in Sr 2 MgSi 2 O 7 :Eu 3þ phosphor. Photoluminescence measurements showed that the phosphor exhibited strong emission peak with good intensity, corresponding to 5 D 0 / 7 F 2 (613 nm) red emission and weak 5 D 0 / 7 F 1 (590 nm) orange emission. The excitation spectra monitored at 613 nm show broad band from 220 to 300 nm ascribed to OeEu charge-transfer band (CTB) centered at about 269 nm, and the other peaks in the range of 300e400 nm originated from fef transitions of Eu 3+ ions. The strongest band at 395 nm can be assigned to 7 F 0 / 5 L 6 transition of Eu 3þ ions due to the typical fef transitions within Eu 3þ of 4f 6 configuration.
Luminescence : the journal of biological and chemical luminescence, 2015
A europium (Eu)-doped di-calcium magnesium di-silicate phosphor, Ca2 MgSi2 O7 :Eu(2+) , was prepared using a solid-state reaction method. The phase structure, particle size, surface morphology, elemental analysis, different stretching mode and luminescence properties were analyzed by X-ray diffraction (XRD), transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM) with energy dispersive X-ray spectroscopy (EDX), Fourier transform infrared (FTIR) spectroscopy, photoluminescence (PL) and mechanoluminescence (ML). The phase structure of Ca2 MgSi2 O7 :Eu(2+) was an akermanite-type structure, which belongs to the tetragonal crystallography with space group P4̅21 m; this structure is a member of the melilite group and forms a layered compound. The surface of the prepared phosphor was not found to be uniform and particle distribution was in the nanometer range. EDX and FTIR confirm the components of Eu(2+) -doped Ca2 MgSi2 O7 phosphor. Under UV excitation...
Origin of saturated green emission from europium in zinc thiogallate
Optical Materials Express, 2013
Europium doped zinc thiogallate, ZnGa 2 S 4 :Eu 2+ , has been reported as a saturated green emitting phosphor, suitable as conversion phosphor in white LEDs for lighting or displays. Up to now, no direct proof for the incorporation of Eu 2+ in ZnGa 2 S 4 has been given. We combined X-ray diffraction (XRD), cathodoluminescence in electron microscopy (SEM-CL) and X-ray absorption spectroscopy (XAS) to study the incorporation of the europium ions in the host material. The previously reported green luminescence was found to originate from small amounts of unintentionally formed EuGa 2 S 4 , and not from europium ions incorporated into ZnGa 2 S 4 . EuGa 2 S 4 has a low quantum efficiency (< 20%) and shows strong thermal quenching, already below room temperature. The XAS data analysis suggests that a certain amount of europium might occupy octahedral voids inside the zinc thiogallate lattice in a divalent state. The zinc ion next to these interstitial dopants is then removed for charge compensation. Notwithstanding the possible, but limited, incorporation of Eu 2+ in ZnGa 2 S 4 , these ions do not activate any luminescence as was shown with SEM-CL.
Structure and luminescence of (Ca,Sr) 2 SiS 4 : Eu 2+ phosphors
Journal of Physics D: Applied Physics, 2010
Sr 2 SiS 4 :Eu 2+ , Ca 2 SiS 4 :Eu 2+ and the solid solution of both, europium-doped (Ca,Sr) 2 SiS 4 , were investigated as UV-VIS excitable green to red powder phosphors. Sr 2 SiS 4 :Eu 2+ shows two emission bands, peaking at 480 nm and 550 nm. By changing the ratio between Ca 2+ and Sr 2+ , the photoluminescent emission spectrum can be tuned. Using X-ray diffraction, the phase composition and lattice parameters of the thiosilicate compounds were determined. The material forms a single, monoclinic Sr 2 SiS 4 -like phase up to 40% substitution of Sr 2+ by Ca 2+ . From 50% to 90% of substitution by Ca 2+ , phase separation was observed, leading to more complex emission spectra.
Acta Physica Polonica A, 2022
The results of synthesis, crystal structure characterization, and luminescence properties study of pure and Eu 3+-doped K0.45Bi0.55Mo0.9V0.1O4 solid solutions have been reported. The obtained powders crystallize in a compact form with an average size of the particles of about 5-10 µm. It was found that doping with europium leads to the transformation of the host from monoclinic to tetragonal scheelitelike phase. The Eu 3+-doped samples reveal intensive red luminescence under excitation in ultraviolet and blue spectral regions. Energy transfer from molybdate-vanadate host to Eu 3+ ions takes place in the studied solid-solution. Intensity of the red luminescence increases when Eu 3+ content increases and no concentration quenching has been found.
Journal of Alloys and Compounds, 2012
Eu 2+ and Eu 2+ -Mn 2+ codoped (Ba,Sr)Mg 2 Al 6 Si 9 O 30 phosphors have been synthesized by solid state reaction, and their luminescent properties are investigated. Under the excitation of 330 nm, it is observed that the emission of Eu 2+ consists of two emission bands, located at around 370 and 450 nm, which are attributed to two Eu 2+ centers (Eu 2+ (I) and Eu 2+ (II)) ions substituting for two different Ba 2+ and Mg 2+ sites, respectively. As Sr 2+ gradually substitutes Ba 2+ , the emission bands of Eu 2+ (I) shift to longer wavelength whereas the emission bands of Eu 2+ (II) exhibit no change. This phenomenon is discussed in terms of the crystal-field strength. A detail analysis on the energy transfer from Eu 2+ to Mn 2+ in SrMg 2 Al 6 Si 9 O 30 host is presented, which indicates the energy of the red emission of Mn 2+ is derived mainly from Eu 2+ (I). We have also demonstrated that BaMg 2 Al 6 Si 9 O 30 :Eu 2+ , Mn 2+ exhibits better thermal quenching properties than that of SrMg 2 Al 6 Si 9 O 30 :Eu 2+ , Mn 2+ because of bigger activation energy.
Research on Chemical Intermediates, 2014
Sr 2 MgSi 2 O 7 :Eu 2? , Dy 3? and Ca 2 MgSi 2 O 7 :Eu 2? , Dy 3? phosphors were synthesized by the high-temperature solid-state reaction method. The phase structure of the prepared phosphors was of akermanite type, which belongs to the tetragonal crystallography. The EDX and FTIR spectra confirm the presence of elements in prepared phosphors. Sr 2 MgSi 2 O 7 :Eu 2? , Dy 3? and Ca 2 MgSi 2 O 7 :Eu 2? , Dy 3? phosphors would emit blue and green light; the main emission peaks that appeared at 465 and 535 nm belong to the broad emission band ascribed to the 4f 6 5d 1 ? 4f 7 transition. Decay graph indicates that both the phosphors have fast decay and slow decay. Investigation into afterglow property showed that the Sr 2-MgSi 2 O 7 :Eu 2? , Dy 3? phosphor held better afterglow property than Ca 2 MgSi 2 O 7 :-Eu 2? , Dy 3? phosphors. ML measurements showed a linear increase in the ML intensity with the impact velocity of the moving piston.