Mechanism of the Luminescence Enhancement of SrSi2N2O2:Eu2+ Phosphor via Manganese Addition (original) (raw)
Related papers
Mechanism of the Luminescence Enhancement of SrSi2N2O2:Eu2+ Phosphor via Manganese Addition
Journal of Physical Chemistry C, 2022
The addition of Mn-O-based compounds during the solid-state synthesis of SrSi 2 N 2 O 2 :Eu 2+ significantly increases the luminescence intensity of this phosphor. Hitherto, this effect was explained as the energy transfer between Eu 2+ and Mn 2+ ions. Using electron paramagnetic resonance and optical techniques, we show that Mn is not incorporated into the SrSi 2 N 2 O 2 host; nevertheless, attempts to dope improve the luminescence quantum yield (QY) of this compound. Moreover, we found that codoping exertion with Mn ions in the synthesis process may also cause the enhancement of persistent luminescence and mechanoluminescence. It is also shown that the structure of the primary defects in SrSi 2 N 2 O 2 :Eu 2+ does not change by adding Mn during the synthesis of this oxynitridosilicate, except their concentration. The changes of the radiative decay time of Eu 2+ induced by attempts of codoping are responsible for the observed increase of the luminescence QY of this phosphor.
Luminescence properties of SrSi2O2N2 doped with divalent rare earth ions
Journal of Luminescence, 2006
The optical properties of SrSi 2 O 2 N 2 doped with divalent Eu 2+ and Yb 2+ are investigated. The Eu 2+ doped material shows efficient green emission peaking at around 540 nm that is consistent with 4f 7 -4f 6 5d transitions of Eu 2+ . Due to the high quantum yield (90%) and high quenching temperature (4500 K) of luminescence, SrSi 2 O 2 N 2 :Eu 2+ is a promising material for application in phosphor conversion LEDs. The Yb 2+ luminescence is markedly different from Eu 2+ and is characterized by a larger Stokes shift and a lower quenching temperature. The anomalous luminescence properties are ascribed to impurity trapped exciton emission. Based on temperature and time dependent luminescence measurements, a schematic energy level diagram is derived for both Eu 2+ and Yb 2+ relative to the valence and conduction bands of the oxonitridosilicate host material. r
The influence of Na2CO3 flux on photoluminescence properties of SrSi2O2N2:Eu2+ phosphor
Ceramics International, 2017
Europium doped oxynitride phosphors Sr 1−x Eu x Si 2 O 2 N 2 (x = 0.04), without and with 3 and 5 wt% Na 2 CO 3 as a fluxing agent were made by a solid state reaction method at 1450°C for 4 h in a flowing nitrogen atmosphere. It has been found that addition of flux results in a lower crystallinity and reduction of phosphor particles diameter to the average level of 8 µm. Analysis of the emission spectra indicates, that they show broad emission bands covering the whole visible range upon UV excitation and that the emission band peaks at 540 nm, without a detectable blue or red shift. The variation in flux concentration proved, that a substantial, four times improvement of the photoluminescence properties were obtained for the sample made with 5 wt% of Na 2 CO 3 addition. Thermal quenching studies elucidated, that for those samples made with a flux the T 1/2 point was not reached before 500 K apart from the notably temperature quenching. This finding proves the economically attractive method for manufacturing strontium oxynitride phosphor with an excellent emission characteristic and a reasonable thermal quenching temperature for application in LEDs.
Luminescence Properties of Sr2MgSi2O7:Eu2+, Ce3+ Phosphor by Solid State Reaction Method
Physics Procedia, 2015
The Sr 2 MgSi 2 O 7 :Eu 2+ , Ce 3+ phosphor was prepared by solid state reaction method, boric acid (H 3 BO 3) was added as flux. The phase structure of Sr 2 MgSi 2 O 7 :Eu 2+ , Ce 3+ phosphor was akermanite type structure which belongs to the tetragonal crystallography with space group P4̅ 2 1 m, this structure is a member of the melilite group and forms layered compound. EDX and FTIR spectra confirm the present elements in Sr 2 MgSi 2 O 7 :Eu 2+ , Ce 3+ phosphor. Three peaks in excitation spectra were found at 253, 293, 325nm and corresponding emission peak was recorded at 465nm, belonging to the broad emission ascribed to the 4f 6 5d 1 →4f 7 transition of Eu 2+. The ML intensity of prepared phosphor was increasing linearly with increases of mechanical load.
Study of the electronic structure and luminescence of Mn-doped SrS phosphors
Journal of the Korean Physical Society, 2012
In this paper, the electronic structure and the luminescence properties of Mn (1 mole%)-doped SrS phosphors synthesized by using the solid state diffusion method are reported. The X-ray diffraction pattern reveals a single-phase rocksalt structure, and the average crystallite size calculated using a Williamson-Hall plot is 72 nm. The near-edge X-ray absorption fine structure (NEXAFS) collected at Mn L3,2-edges confirms the presence of divalent Mn in SrS. A bright green photoluminescence (PL) at 547 nm is observed at an excitation wavelength of 355 nm, which may be attributed to the 4 T1 − 6 A1 inner atomic transition of the 3d electrons in the Mn 2+ ion under the cubic crystal field of SrS. We have also studied the thermoluminescence (TL) of UV (254 nm)-irradiated Mn-doped SrS phosphors. The TL glow curve has a well-resolved single peak around 360 K, which shifts slightly to lower temperatures with increasing UV exposure time, confirming second-order kinetics. A kinetic analysis of the experimental TL glow curve has been carried out using Chen's peak shape method to determine the trapping parameters.
Journal of Materials Science: Materials in Electronics, 2016
Sr 2 MgSi 2 O 7 :Eu 3? and Sr 2 MgSi 2 O 7 :Eu 3? , R ? (R ? = Li ? , Na ? and K ?) phosphors were prepared by conventional solid state reaction method. The crystal structures of synthesized phosphors were an akermanite type structure which belongs to the tetragonal crystallography. The thermoluminescence kinetic parameters such as activation energy, order of kinetics and frequency factor was calculated by peak shape method. In this work, the orangered emission originated from the 5 D 0-7 F J (J = 0, 1, 2, 3, 4) transitions of Eu 3? ions could clearly be observed after samples were excited at 395 nm. Decay graph indicate that these phosphors also contain the fast and slow decay process. Mechanoluminescence intensity of prepared Sr 2 MgSi 2 O 7 :Eu 3? and Sr 2 MgSi 2 O 7 :Eu 3? , R ? (R ? = Li ? , Na ? and K ?) phosphors were increases linearly with the increasing impact velocity of moving piston (load). CIE color chromaticity diagram confirm that the prepared phosphors would emit orange-red color. Thus the present investigation indicating that this phosphor may be a potential candidate for stress sensors. The dopant R ? (R ? = Li ? , Na ? and K ?) as charge compensator in Sr 2 MgSi 2 O 7 :Eu 3? can further enhance luminescence intensity, and the emission intensity of Sr 2 MgSi 2 O 7 :Eu 3? doping Li ? is higher than that of Na ? or K ? .
Journal of Materials Science: Materials in Electronics, 2015
A series of rare earth doped and co-doped distrontium magnesium di-silicate phosphors namely: Sr 2 MgSi 2 O 7 :Ce 3? , Sr 2 MgSi 2 O 7 :Eu 2? and Sr 2 MgSi 2 O 7 :Eu 2? , Ce 3? were prepared by the solid state reaction method. The crystal structures of sintered phosphors were an akermanite type structure which belongs to the tetragonal crystallography. The chemical compositions of sintered phosphors were confirmed by energy dispersive X-ray spectroscopy (EDS). Under the ultraviolet excitation, the emission spectra of both Sr 2 MgSi 2 O 7 :Eu 2? and Sr 2 MgSi 2 O 7 :Eu 2? , Ce 3? phosphors were composed of a broad band peaking at 460 nm, belonging to the broad emission band. When the Sr 2 MgSi 2 O 7 :Eu 2? phosphor is co-doped with Ce 3? ions, thermouminescence, photoluminescence, afterglow and mechanoluminescence (ML) intensity were strongly enhanced. The Sr 2 MgSi 2 O 7 :Eu 2? phosphor showed some afterglow with short persistence time. By incorporation of Ce 3? ions, an efficient energy transfer from Ce 3? to Eu 2? was found and emission intensity of Sr 2 MgSi 2 O 7 :Eu 2? was enhanced. The ML intensities of Sr 2 MgSi 2 O 7 :Ce 3? , Sr 2 MgSi 2 O 7 :Eu 2? and Sr 2 MgSi 2 O 7 :Eu 2? , Ce 3? phosphors were proportionally increased with the increase of impact velocity, which suggests that these phosphors can be used as sensors to detect the stress of an object. Thus the present investigation indicates that the piezoelectricity is responsible to produce ML in prepared phosphors.
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.
Solid state synthesis of SrAl2O4:Mn2+ co-doped with Nd3+ phosphor and its optical properties
Journal of Luminescence, 2013
The optical properties of alkaline earth aluminates doped with rare earth ions have received much attention in the last years and this is due to their chemical stability, long-afterglow (LAG) phosphorescence and high quantum efficiency. However, there is a lack of understanding about the nature of the rare earth ion trapping sites and the mechanisms which could activate and improve the emission centers in these materials. Therefore a new phosphor material composition, SrAl 2 O 4 :Mn 2+ , co-doped with Nd 3+ was synthesized by a traditional solid-state reaction method. The influence of transition metal and rare earth doping on crystal structure and its luminescence properties have been investigated by using X-ray diffraction (XRD), Raman scattering, Photoluminescence (PL) and Radioluminescence (RL). Analysis of the related diffraction patterns has revealed a major phase characteristic of the monoclinic SrAl 2 O 4 compound. Small amounts of the dopants MnCO 3 and Nd 2 O 3 have almost no effect on the crsytalline phase composition. Characteristic absorption bands from Nd 3+ 4f-4f transitions in the spectra can be assigned to the transitions from the ground state 4 I 9/2 to the excited states. The luminescence of Mn 2+ activated SrAl 2 O 4 exhibits a broad green emission band from the synthesized phosphor particles under different excitation sources. This corresponds to the spin-forbidden transition of the d-orbital electron associated with the Mn 2+ ion. In photo-and radio-luminescence spectra, Nd 3+ 4f-4f transition peaks were observed. The emitted radiations for different luminescence techniques were dominated by 560, 870, 1057 and 1335 nm peaks in the visible and NIR regions as a result of 4 I 9/2 -4 G 7/2 and 4 F 3/2 -4 I J (J ¼9/ 2, 11/2 and 13/2) transitions of Nd 3+ ions, respectively. Multiple emission lines observed at each of these techniques are due to the crystal field splitting of the ground state of the emitting ions. The nature of the emission lines is discussed.