Transition Mn Research Articles

Mn-doped CsPbCl3 perovskite quantum dots (PQDs) incorporated into silica/alumina particles used for WLEDs

Recently, more and more scholars synthesised the Mn-doped CsPbX3 (X = Cl, Br, I) inorganic perovskite quantum dots (PQDs), which exhibited a strong dopant luminescence characteristic of d-d transition of Mn2+ and dual-color emission. However, Mn-doped CsPbCl3 PQDs suffer from the instability, which hindered the application of PQDs in optoelectronic devices. Here, we resolve this problem with SiO2/Al2O3 monolith (SAM) through a simple sol-gel process and obtained a robust luminescent PQDs-SiO2/Al2O3 monolith (PQDs-SAM) with surprising high stability. This is an easy one-pot operation and can be done with large quantities. The composites not only maintain the PQDs remarkable optical properties, but also improve their stability, which is significantly. The Mn-doped CsPbCl3 PQDs-SAM in powder form is easily mixed into the resins and applied as color-converting layer with curing on blue light-emitting diodes (LED). And above all, the orange PQDs-SAM composite is used as red phosphor and stack on the Ce3+:YAG phosphor-in-glass (Ce-PiG) via screen-printing technology (Ce-PiG&R-PQDs-SAM). Whereafter, warm WLED is constructed by blending the Ce-PiG&R-PQDs-SAM materials with the InGaN blue chips. And the constructed WLEDs generate a warm white with an optimal luminous efficacy (LE) of 80.91 l m/W, a high CRI of 83.8, and a low CCT of 4082 K.

Controlling Blue and Red Light Emissions from Europium (Eu2+)/Manganese (Mn2+)-Codoped Beta-Tricalcium Phosphate [β-Ca3(PO4)2 (TCP)] Phosphors

Tunable light emission from europium (Eu2+)/manganese (Mn2+)-codoped beta-tricalcium phosphate [β-Ca3(PO4)2 (TCP)] has been investigated as a function of the Mn2+ and Eu2+ concentrations and annealing temperature. Eu2+/Mn2+-doped TCP phosphor (Eu/Mn-TCP) was synthesized by coprecipitation method followed by thermal annealing at temperature up to 1100°C. The Eu2+/Mn2+-doped TCP particles have diameter of about 1 μm. The light emission from TCP is enhanced in the sample with 7.5 mol.% Mn2+ and 0.3 mol.% Eu2+ annealed in Ar + 5% H2 atmosphere at 1100°C. The blue band at 430 nm is attributed to the 4f6 5d1–4f7 transition of Eu2+. The sharp peak at 660 nm is ascribed to the 4T1–6A1 transition of Mn2+ in TCP. These results suggest codoping of Eu2+/Mn2+ to TCP phosphor to obtain β-Ca3(PO4)2:Eu2+,Mn2+ phosphors with tunable luminescence, having potential applications in agricultural lighting.

Photoluminescence and cathodoluminescence of Mn doped zinc silicate nanophosphors for green and yellow field emissions displays

Mn2+-doped Zn2SiO4 (ZSM2+) was synthesized by a facile sol–gel technique. The obtained samples were characterized by X-ray diffraction (XRD), Raman spectroscopy, photoluminescence (PL) and cathodoluminescence (CL) techniques. Under UV excitation, spectra showed that the α-ZSM2+ phosphor exhibited a strong green emission around 525 nm and reached the highest luminescence intensity with the Mn doping concentration of 5 at.%. However, for the β-ZSM2+ phase, an interesting yellow emission band centered at ~ 575 nm of Mn2+ at the Zn2+ tetrahedral sites was observed. In addition, an unusual red shift with increasing Mn2+ content was also found and attributed to an exchange interaction between Mn2+. Both PL and CL spectra exhibit an intense green and yellow emission centered at ~ 525 and ~ 573 nm, respectively, due to the 4T1 (4G)-6A1 (6S) transition of Mn2+. Furthermore, these results indicated that the Mn2+-doped zinc silicate phosphors may have potential applications in green and yellow emissions displays like field emission displays (FEDs).

Two-Step Synthesis and Surface Modification of CaZnOS:Mn2+ Phosphors and the Fabrication of a Luminescent Poly(dimethylsiloxane) Film.

The CaZnOS:Mn2+ (CZOSM) phosphor has been extensively studied for its excellent optical performance, with a typical red emission band peaking at about 580 nm ascribed to the 4T1(4G)-6A1(6S) transition of Mn2+. Herein the CZOSM phosphor was synthesized by a novel two-step method accompanied by control of the morphology of the precursor in the first step followed by sintering in the second step, which demonstrated improved emission intensity and uniform morphology simultaneously compared to those obtained by the traditional solid-state reaction route. Thus, uniform ZnS:Mn2+ particles could be obtained by a hydrothermal method, and then a Ca(OH)2 shell was coated onto the ZnS:Mn2+ particles via a precipitation reaction. After that, these mixtures were sintered at the optimum temperature 800 °C in an argon atmosphere to prepare the CZOSM particles. Oleic acid (OA) was further used to transfer the hydrophilic CZOSM phosphors to hydrophobic ones. Finally, luminescent poly(dimethylsiloxane) (PDMS) films were fabricated by using the hydrophobic CZOSM@OA powders, and their optical performance and flexibility were evaluated. Our results provide insight into the synthesis of hydrophobic phosphor particles used in luminescent PDMS films and help to unravel their potential application for flexible optical devices.

Ln3Al5O12:Mn4+ (Ln = Y and Lu): non-rare-earth doped red phosphor for improving light properties of white light emitting diodes

We fabricated a series of Y3Al5O12:Mn4+ and Y1−yLuyAl5O12:Mn4+ phosphors by a solid state reaction. The phase and the optical properties of the synthesized phosphors were investigated. Under the excitation at 465 nm, Y3Al5O12:Mn4+ phosphors show emission bands locating at deep red regions, which is induced by the spin- and parity-forbidden 2Eg → 4A1g transitions of Mn4+. The substitution of Y3+ by Lu3+ decreases the lattice parameter and thus strengthens the crystal field strength, which gives rise to the blue shift of emission band for Y1−yLuyAl5O12:Mn4+ phosphors. Due to the compensation of red light by Y3Al5O12:Mn4+ or Y1−yLuyAl5O12:Mn4+ phosphor, the values of correlated-color-temperature for fabricated LEDs are decreased, which leads to the suitable application for them in indoor illumination.

Preparation of Mg1+yAl2-xO4:xMn4+, yMg2+ deep red phosphor and their optical properties

Exploration of efficient deep red phosphor based on non-rare-earth ion activated oxide is of great practical value in the field of phosphors converted white light-emitting diode lighting. A spinel Mg1+yAl2-xO4:xMn4+, yMg2+ phosphor with deep red emission is synthesized by a solid-state reaction route. The crystal structure and morphology are characterized by powder X-ray diffraction and scanning electron microscopy. The luminescent performance is characterized by fluorescence spectrophotometer and fluorescence decay curves. The results demonstrate that the synthesized phosphor shows that two excited spectrum bands centered at 290 nm and 438 nm cover a broad spectral region from 220 nm to 500 nm due to the Mn4+-O2- charge transfer band and the 4A2-4T1 and 4T2 transitions of Mn4+ ions. Upon excitation at 300 nm, a strong, narrow red emission band is observed between 600 and 700 nm peaked at 652 nm as a result of the spin-forbidden 2Eg-4A2g electron transition of Mn4+. The corresponding chromaticity coordinate is (0.7256, 0.2854). Additionally, the concentration quenching of Mn4+ in the MgAl2O4 host is evaluated in detail, which indicates that the optimum doping concentration of Mn4+ is experimentally determined to be 0.14 mol%. The critical distance is calculated to be 52.15 according to the Blasse equation, which elucidates that the concentration quenching mechanism is consequently very likely to be induced by the multipole-multipole interaction. The crystal field strength (Dq) and the Racah parameters (B and C) are estimated to evaluate the nephelauxetic effect of Mn4+ suffered in MgAl2O4:Mn4+ host lattice. Luminous mechanism is explained by Tanabe-Sugano energy level diagram of Mn4+ ion. The ratio of Dq/B equals 1.74, indicating that Mn4+ ions experience a weak crystal field in the MgAl2O4 host and emission peak energy of 2Eg-4A2g transition is dependent on the nephelauxetic effect. The red emission intensity of Mg1+yAl2-xO4:xMn4+, yMg2+ increases on account of excess Mg2+ which would compensate for the local charge balance surrounding Mn4+ ions, furthermore, lead the Mn4+-Mn4+ pairs connected with interstitial O2- to transform into isolated Mn4+ ions, and thus eliminating energy transfer and enhancing the luminescence efficiency effectively. The decay times of two time-dependent curves of Mg1+yAl2-xO4:xMn4+,yMg2+ are 0.672 ms and 0.604 ms, and each entire decay curve could be well-fitted to single-exponential, confirming that there is only a single Mn4+ ion luminescence center. The decay time of Mn4+ luminescence is prolonged with the increase of Mg2+ content, indicating that excitation energy transfer and non-radiative relaxation between Mn4+-Mn4+ pairs decrease, the reason is that photoexcitation energy can be temporarily stored in the trapping centers induced by excess positive charges. These results imply that Mn4+ doped Mg1+yAl2 -xO4:xMn4+, yMg2+ is a promising candidate of deep-red phosphors for near-UV and blue light emitting diodes. These findings in the paper would be beneficial not only to developing a low-cost and safe strategy to produce high-efficient Mn4+ activated luminescent materials for white light emitting diodes, but also to providing a new insight into improving the photoluminescence properties of Mn4+.

Green and yellow luminescence properties of Willemite Zn2SiO4 nanocomposites by sol–gel method

Nanoparticles of willemite, α-Zn2SiO4 have been prepared by a sol–gel method. These samples were prepared by a simple solid-phase reaction under natural atmosphere at 1200 °C after the incorporation of ZnO:Mn and ZnO:V nanoparticles in silica monolith. The nanophosphors powder samples were characterized using X-ray diffraction, transmission electron microscopy (TEM) and photoluminescence (PL) spectroscopy. XRD analysis revealed that the α-Zn2SiO4 phase was at 1200 °C. In addition, the PL spectrum for the α-Zn2SiO4:Mn nanocomposite showed that a dominant peak at 525 nm which is due to4T1–6A1 transitions of Mn2+ ions. In the case of α-Zn2SiO4:V, the PL had shown a band centered around 540 nm. This band is due to the V in the interfaces between Zn2SiO4 particles and SiO2 host matrix. The findings of this work are very promising and can justify the use of these novel materials as a potential candidate in the field of photonic applications.

Influence of preparative conditions for obtaining ZnS:Mn nanoparticles using ultrasound-assisted precipitation

Nanocrystalline manganese-doped zinc sulphide (ZnS:Mn) phosphor powders were prepared by ultrasound-assisted precipitation, using the simultaneous addition of reagents under controlled constant flow. The precipitation process was optimised at low temperature (40 °C), using variable concentrations of reagents, with or without diheptyl sodium sulphosuccinate as surfactant. Complementary investigations such as thermal analysis, X-ray diffraction, SEM, TEM and BET were used to characterise the phosphors. Photoluminescence spectra show a strong orange emission with a maximum centred at 590 nm due to the electronic transitions of Mn2+ ions occupying Zn2+ sites in the host lattice. Correlation of preparative conditions with morphostructural and luminescent characteristics enables us to determine the optimal conditions for the preparation of ZnS:Mn nanoparticles with crystallite size in the range of 1.4–2.8 nm. ZnS:Mn nanopowder with nanoparticle size of ~ 2.5 nm, precipitated from diluted reactant solution in the presence of 5.0 g/L of diheptyl sodium sulphosuccinate, displays the highest photoluminescence.

Fabrication of core/shell structured SiO2/Zn2SiO4:Mn2+ composite and its photoluminescence properties

Core/shell structured SiO2/Zn2SiO4:Mn2+ composite was prepared by thermal-diffusion reaction between SiO2 and Zn1−xMnxO particles, which is a low cost solid-state method. The X-ray diffraction and scanning electron microscope results showed that a 5-μm-thick dense Zn2SiO4:Mn2+ layer was successfully formed on the surface of the SiO2 particles. The PL spectrum of the SiO2/Zn2SiO4:Mn2+ composite revealed a green emission peak at 526 nm with PL intensity 20% higher than that of the conventional Zn2SiO4:Mn2+ particles. In addition, the decay time of the SiO2/Zn2SiO4:Mn2+ composite was shorter (τ 10% = 7 ms) than that of the conventional Zn2SiO4:Mn2+ particles (τ 10% =12 ms), which is owing to the relaxation of forbidden transition of Mn2+ ions due to the localized stress of Mn2+ ions arising from the surface tension in the SiO2/Zn2SiO4:Mn2+ composite.

Low temperature photoluminescence study of Mn-doped ZnSe nanocrystals

In the present work, photoluminescence and photoluminescence excitation (PLE) spectroscopy have been employed to study d-d and p-d exchange interaction of Mn-doped ZnSe nanocrystals (NCs) from room temperature through 10K. Mn-doped ZnSe NCs of size about 5nm with zinc blend crystal structure are grown by the nucleation doping strategy. The doped-NCs reveal strong Mn-related emission; surprisingly that shows red shift with the decrease in temperature. At 10 K, four different excitation features related to d-d transitions of Mn2+ were observed. Crystal field parameter (Dq) and Racah parameters (B and C) are calculated using low temperature PLE spectra recorded by fixing the Mn2+related orange luminescence emission. Increased covalency of the metal-ligand bond and the enhanced exchange interaction between different d-electrons is found. Increment in covalency and exchange interaction is corroborated by the appearance of broad feature in electron spin resonance spectroscopy.

Solid state synthesis, luminescent properties and energy transfer from Eu2+ to Mn2+ in red phosphor BaMg2Si2O7:Eu2+,Mn2+

A series of red phosphors Ba1-yMg2-xSi2O7: xMn2+,yEu2+ have been synthesized by solid-state reaction at 1200 °C for 4 h under H2 atmosphere. The crystal structure and photoluminescence properties have been measured and analyzed. Under excitation of 342 nm, Eu2+ doped Ba1-yMg2Si2O7 (y = 0.05–0.06) shows violet emission at 400 nm, which is due to the 4f–5d transition of Eu2+, while Mn2+ doped BaMg2-xSi2O7 (x = 0.02–0.40) shows weak reddish emission with a broad band centered at around 640 nm, which is caused by the 4T1(4G) -6A1(6S) transitions of Mn2+. When Eu2+ and Mn2+ were co-doped, excellent red emission is shown under the n-UV excitation. Eu2+ and Mn2+ co-doped BaMg2Si2O7 phosphor shows two intense emission bands with the peak at 400 nm and 660 nm, respectively. The broad emission band for Eu2+ overlaps with the excitation peaks of Mn2+ in the range of 400–450 nm, which shows that the emission of Mn2+ is dominantly ascribed to the persistent energy transfer from Eu2+. By changing the ratio of Eu2+/Mn2+, the emission color can be tuned from violet to red. When the doping content is fixed at 0.16 for Mn2+ and 0.32 for Eu2+, the CIE of the phosphor is (0.495,0.315). Eu2+ and Mn2+ co-doped BaMg2Si2O7 phosphors may have potential application for near-UV light-emitting diodes.

Ce3+-sensitized red Mn2+ luminescence in calcium aluminoborate phosphor material

Ce3+ doped and Ce3+,Mn2+ co-doped calcium aluminoborate (CAB) phosphors were synthesised by solid-state reaction method and their optical properties were studied. X-ray powder diffraction, SEM and TEM studies indicated the crystallization of the main trigonal CaAl2B2O7 phase and the presence of an additional non-crystalline phase. It was also observed that increasing dopant concentration promotes phase separation. Hence, both series of phosphors demonstrated the changes in luminescence properties via activator concentration variation. Upon UV excitation (λex = 310 nm) Ce3+ doped and Ce3+,Mn2+ co-doped materials yielded intensive blue and pinkish luminescence, respectively. The spectra of CAB:Ce3+ samples showed a broad emission band due to 5d→4f transition of Ce3+, which broadened and shifted to longer wavelengths with increasing dopant content. Mn2+ co-doping caused appearance of another broad-band emission with a maximum of 680 nm, resulting from the 4T1(4G) →6A1(6S) transition of Mn2+. Detailed analysis of the emission and excitation spectra as well as decay time traces as a function of dopant concentration showed that efficient resonant energy transfer mainly occurs between Ce3+ and Mn2+ incorporated in the non-crystalline phase in CAB material. The estimated values of energy transfer efficiency of CAB:Ce3+(3%),Mn2+(4%) is close to 52%.

Photoluminescence and cathodoluminescence properties of green–red emitting ZnGd4Si3O13: Tb3+, Mn2+ phosphors

The photoluminescence and cathodoluminescence properties of new silicate oxyapatite phosphors ZnGd4Si3O13: Tb3+, Mn2+ were investigated in this study. The Rietveld refinement indicated that the prepared phosphors exhibited a hexagonal structure with space group P63/m (no. 176). Under UV excitation, ZnGd4Si3O13: Mn2+ phosphors presented a red emission band due to the T1(4G)–6A1(6S) transition of Mn2+ ions, while ZnGd4Si3O13: Tb3+ showed several emission lines at 490, 544, 585 and 621 nm attributed to the 5D4→7FJ (J = 6, 5, 4, 3) transitions of Tb3+ ions. The co-doping of Tb3+ ions into ZnGd4Si3O13: Mn2+ resulted in a 100% enhancement of the photoluminescence intensity for Mn2+ ions through a dipole–dipole energy transfer mechanism. On the other hand, the energy transfer process from the sensitizers (Tb3+) to the activators (Mn2+) led to a decrease in Tb3+ emission as co-doping Mn2+ ions into ZnGd4Si3O13: Tb3+. Increasing the concentration of Mn2+ ions from x = 0.02 to x = 0.08 for Zn2−xMnxGd3TbSi3O13 efficiently enhanced the energy transfer efficiency from 90 to 98%. Under the electron-beam excitation, the emission spectra of phosphors were similar to those observed under UV excitation. However, a deviation of CIE coordinates was found under the electron-beam excitation due to the relatively unapparent energy transfer between Tb3+ and Mn2+ ions. The present results suggested a new series of color-tunable phosphors which can be used for both photoluminescence and cathodoluminescence applications.

Effects of flux on the luminescence of MgGa2O4:Mn2+ phosphors

The effects of H3BO3 and MgF2 fluxes on the crystal structure and photoluminescence (PL) of MgGa2O4:Mn2+ phosphors were investigated. The PL excitation spectra of the powders consisted of intensive broad bands (∼290nm), and sharp peaks at longer wavelengths. The former could be attributed to charge transfer between the Mn2+ and O2− ions, referred to as charge transfer band (CTB), while the latter was attributed to the d–d transitions of Mn2+ ions. Under CTB excitation, the PL spectra exhibited green emission peaks at 505nm, assignable to the 4T1(4G) → 6A1(6S) transition of Mn2+ ions in tetrahedral sites. Compared to MgF2, H3BO3 was more favorable for phase formation, higher crystallinity, and particle size enlargement, thus resulting in a significant enhancement in the emission intensity. The Mn2+ concentration affected the CTB and the crystal structure; the strongest emission intensity was observed for a high Mn2+ concentration of 0.5mol%.

Deep red BaTiF4:Mn4+ phosphor: synthesis, optical properties and application for warm WLED devices

Non-rare-earth based red phosphor discovery is of great interest in the field of energy-efficient WLED lighting. In this work, we give the hydrothermal synthesis of BaTiF4:Mn4+ phosphor. The phase and microstructure of the obtained BaTiF4:Mn4+ phosphors have been investigated with the aids of X-ray diffraction spectroscopy and scanning electronic microscope. Under the excitation of blue light, BaTiF4:Mn4+ phosphors exhibit red emission originating from the \(^{2}{{E}_{g}}{{\to }^{4}}{{A}_{2g}}\) transitions of Mn4+ ions. Simultaneously, the concentration and thermal quenching also have been investigated systematically, and the quenching mechanism has been elucidated in detail. Employing BaTiF6:Mn4+ as red phosphor, we fabricate a high-performance WLED with a low correlated color temperature of 3857 K and a high color rendering index of 85.3. Based on the improvement of correlated color temperature and color rendering index, the BaTiF6:Mn4+ red phosphors supplement the deficiency of WLEDs fabricated by combining blue chip and only YAG:Ce3+, which suggest that it is a promising commercial red phosphor in warm WLEDs.

Exciton-to-Dopant Energy Transfer in Mn-Doped Cesium Lead Halide Perovskite Nanocrystals.

We report the one-pot synthesis of colloidal Mn-doped cesium lead halide (CsPbX3) perovskite nanocrystals and efficient intraparticle energy transfer between the exciton and dopant ions resulting in intense sensitized Mn luminescence. Mn-doped CsPbCl3 and CsPb(Cl/Br)3 nanocrystals maintained the same lattice structure and crystallinity as their undoped counterparts with nearly identical lattice parameters at ∼0.2% doping concentrations and no signature of phase separation. The strong sensitized luminescence from d-d transition of Mn2+ ions upon band-edge excitation of the CsPbX3 host is indicative of sufficiently strong exchange coupling between the charge carriers of the host and dopant d electrons mediating the energy transfer, essential for obtaining unique properties of magnetically doped quantum dots. Highly homogeneous spectral characteristics of Mn luminescence from an ensemble of Mn-doped CsPbX3 nanocrystals and well-defined electron paramagnetic resonance spectra of Mn2+ in host CsPbX3 nanocrystal lattices suggest relatively uniform doping sites, likely from substitutional doping at Pb2+. These observations indicate that CsPbX3 nanocrystals, possessing many superior optical and electronic characteristics, can be utilized as a new platform for magnetically doped quantum dots expanding the range of optical, electronic, and magnetic functionality.

Synthesis and tunable emission properties of CaZr(PO4)2:Mn2+, Sm3+ phosphor

CaZr(PO4)2:Mn2+ and CaZr(PO4)2:Mn2+, Sm3+ phosphors are synthesized by high-temperature solid state reaction method in air. CaZr(PO4)2:Mn2+ phosphor shows green emission and its broad emission band peaking at ~545 nm within the range 470–650 nm is attributed to the 4T1(G) → 6A1(6S) transition of Mn2+ ion. The optimal Mn2+ doping concentration is ~5 mol% in CaZr(PO4)2:Mn2+ phosphor. CaZr(PO4)2:Mn2+, Sm3+ phosphor with excitation 399 nm emits reddish-orange light, and it shows a systematically varied hue from green to yellow with excitation 405 nm by changing Sm3+ and Mn2+ ions concentration. The luminous mechanism of CaZr(PO4)2:Mn2+, Sm3+ phosphor is analyzed and explained by the simplified energy level diagrams of Mn2+ and Sm3+ ions in CaZr(PO4)2:Mn2+, Sm3+ phosphor. The experimental results are helpful to develop new Mn2+/Sm3+-doped materials.

Long persistent luminescence in Mn^2+-activated sodium gallium germanate glass and glass ceramics induced by infrared femtosecond laser pulses

A distinct long persistent luminescence (LPL) was obtained from home-made Mn2+-activated sodium gallium germanate glass samples which were excited by an infrared femtosecond laser. The LPL, with a central wavelength longer than 600 nm, can be seen by the naked eye for more than one hour in the dark at room temperature. It has been proven that the LPL originated from the 4T1→ 6A1 transition of Mn2+ ions rather than from femtosecond laser induced extrinsic defects with photoluminescence (PL) bands peaking at 1.85 and 2.2 eV. The LPL properties of Mn2+ in the same host glass-ceramics were also investigated. An obvious green emission band appeared in PL spectra while absent in LPL spectra, which indicated a process distinguished from traditional heat-assisted tunneling effect. A new mechanism based on the process of strong-field excitation, collision excitation, electron trapping and direct capture of de-trapped electrons by excited states of Mn2+ ions is proposed to elucidate the generation of LPL.

Synthesis and luminescence properties of NaAl11O17:Mn2+ green phosphor for white LEDs

Novel NaAl11O17:Mn2+ green phosphor is synthesized by solid-state reaction method in air. The emission band peaking at ~508nm is observed owing to the 4T1→6A1(6S) transition of Mn2+ ion, and the chromaticity coordinates are (0.0725, 0.6468). The excitation band peaking at ~360, 382, 424, 450, and 490nm are attributed to 6A1(6S)→4E(4D), 4T2(4D), [4A1(4G), 4E(4G)], 4T2(4G), and 4T1(4G) transitions of Mn2+ ion, respectively, which indicate that NaAl11O17:Mn2+ phosphor may be excited by (near) ultraviolet and blue LED chip. The luminous mechanism is explained by Tanabe–Sugano diagram of Mn2+ ion. The optimal Mn2+ doping concentration is ~3.5mol%. The NaAl11O17:3.5%Mn2+ phosphor shows high quantum efficiency of ~67.84% with excitation 424nm. The lifetime decreases from 6.72 to 6.0ms with increasing Mn2+ concentration in the range of 0–4mol%.

Efficient sensitization of Eu2+/Mn2+ emissions by Ce3+ doping in NaMgPO4 host under UV excitation

A series of Ce3+/Eu2+/Mn2+-tridoped NaMgPO4 phosphors were synthesized using the combustion-assisted synthesis method. The luminescence properties and energy transfer from Ce3+/Eu2+ to Mn2+ in NaMgPO4 host have been studied. Co-doping Ce3+/Mn2+ is proved to be an ineffective approach to enhance the red emission of Mn2+, while effective energy transfer from Eu2+ to Mn2+ occurs in NaMgPO4:Eu2+,Mn2+ due to good spectrum overlap between the emission band of NaMgPO4:Eu2+ and the excitation band of NaMgPO4:Eu2+,Mn2+. NaMgPO4:Eu2+,Mn2+ phosphor shows a blue emission centered at 442 and a red emission peaking at 635 nm, which could be ascribed to the allowed 5d–4f transition of Eu2+ ions and the 4T1(4G)–6A1(6S) transition of Mn2+ ions, respectively. Co-doping Ce3+ ions can greatly enhance both the emission intensities of Eu2+ and Mn2+ ions, which is attributed to an efficient Ce3+ → Eu2+ → Mn2+ energy transfer and an increase in the number of luminescent centers (Eu2+) on Ce doping.