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Abstract A set of Eu3+, Dy3+ and Tb3+ doped novel scheelite-type LiCaGd(WO 4) 3 (LCGW)-based phosphors was prepared via a conventional solid-state reaction method. The X-ray diffraction (XRD), transmission electron microscopy (TEM) analysis, characteristics of luminescence, PL thermostability, decay lifetimes, as well as CIE coordination were investigated to characterize the as-prepared samples in detail. The XRD analysis indicated that the Eu3+, Dy3+ and Tb3+ ions were incorporated into the LCGW host lattice. Under the ultraviolet radiation, the characteristic emission lines of Eu3+ (5D 0 –7F 2), Dy3+ (4F 9/2 –6H 13/2) and Tb3+ (5D 4 –7F 5) ions were observed. The Eu3+ and Tb3+ single-doped LCGW fluorescent powders showed bright red and green emissions, respectively, without concentration quenching. As well as the Dy3+ doped LCGW phosphors radiate a strong yellow light at optimal Dy3+ concentration 0.08 mol. The efficient energy transfer phenomenon was observed for the Eu3+/Dy3+ and Tb3+/Dy3+ ions. The emission color of the LCGW: x Tb3+/0.08Dy3+ samples was tuned from yellow (0.4074, 0.4727) to green (0.3604, 0.5521) via adjusting the Tb3+ concentration. The emission color of LCGW: y Eu3+/0.08Dy3+ can be tuned from yellow (0.491, 0.3856) to red (0.5694, 0.3512) by variation of the Eu3+/Dy3+ ratio. Additionally, the thermal stability of the luminescence in the LCGW phosphors doped by Eu3+, Tb3+, Dy3+ ions was studied. The results verified that the LCGW:Ln3+ (Ln = Tb, Eu, Dy) phosphors are promising for applications in white LEDs. [ABSTRACT FROM AUTHOR]

A series of novel luminescent emission-tunable phosphors Mg 2 La 8 (SiO 4 ) 6 O 2 :Ce 3+ ,Tb 3+ (MLS:Ce 3+ ,Tb 3+ ) have been prepared by a solid-state reaction. The phase formation was firstly confirmed through X-ray diffraction technique and refined by the Rietveld method. The MLS:Ce 3+ ,Tb 3+ phosphors, which crystallized in apatite-type hexagonal phase, exhibited a broad excitation band ranging from 200 to 400 nm and several emission bands centered at 426 nm and 551 nm. Energy transfer from Ce 3+ to Tb 3+ ions via a dipole-dipole mechanism occurred in the as-synthesized phosphors upon ultraviolet (UV) excitation. The energy transfer efficiency increases with increasing doping content of Tb 3+ ions, which was confirmed by the luminescence spectra and fluorescence decay curves of corresponding ions simultaneously. The energy transfer critical distance was calculated and evaluated by both the concentration quenching and spectral overlap methods. The chromaticity of emission-tunable phosphors was also characterized by the Commission International de l'éclairage (CIE) chromaticity indexes, and the color tone can be tuned from blue (0.179, 0.122) to green (0.267, 0.408) by controlling the ratio of Ce 3+ /Tb 3+ . [ABSTRACT FROM AUTHOR]

A series of solid solution phosphors Ca 9 La(PO 4 ) 5 [(Si 1- x Ge x )O 4 ]F 2 :Ce 3+ with apatite structure in the P 6 3 / m space group have been prepared. The novel solid solution phosphors show continuously controlled violet-blue emission. It is found that both substantial spectra broadening (45 → 100 nm) and red-shift (404 → 422 nm) can be realized with the continuous introduction of [GeO 4 ] 4- into the crystal lattice which has been simulated by a crystal-field model. The above results indicate that the tetrahedral substitution is interesting to induce spectral tuning properties based on the chemical composition control of the iso-structural solid solutions. [ABSTRACT FROM AUTHOR]

The structural and luminescence properties of apatite-type compound Mn 2 Gd 8 (SiO 4 ) 6 O 2 have been investigated. The crystal structure of Mn 2 Gd 8 (SiO 4 ) 6 O 2 has been obtained from the X-ray diffraction data by Rietveld method in the hexagonal system, space group P6 3 / m , a = 9.3851 Å, c = 6.7904 Å, V = 517.97 Å 3 , Z = 1. The Mn 2 Gd 8 (SiO 4 ) 6 O 2 phase contains two cationic sites, one site ( 4f site with point symmetry C 3 ) is a distorted tricapped trigonal prismatic polyhedron formed by nine oxygen atoms, and other site ( 6h sites with point symmetry C s ) is an irregular polyhedron of pentagonal bipyramidal geometry with the coordination by seven oxygen atoms. It is found that the Mn 2+ ions occupy only 4f sites with C 3 point symmetry, that has been verified by photoluminescence spectrum and decay curves. This work provides an insight to the novel inorganic compound design and gives an impetus to discover new functional materials and develop new applications. [ABSTRACT FROM AUTHOR]

Tb 3+ –Sm 3+ co-doped Ba 3 NaLa(PO 4 ) 3 F phosphors with apatite structure have been prepared by a high temperature solid-state reaction, and their luminescence properties have been investigated in detail. The energy transfer (ET) mechanism was verified as the dipole–quadrupole mechanism, and the ET efficiency as well as the critical distance is also estimated. As a result of fine-tuning of the emission composition of the Tb 3+ and Sm 3+ ions, tunable luminescence properties can be realized by combining the emission of Tb 3+ and Sm 3+ in a single host lattice under UV light excitation. The emission color of the obtained phosphors can be modulated from green to yellow by controlling the doping content of the Sm 3+ ions with the fixed Tb 3+ content. Additional, as the temperature increases from RT to 150 °C, the PL intensities of Ba 3 NaLa 0.7 (PO 4 ) 3 F:0.10Tb 3+ ,0.20Sm 3+ decreased to 80.4% and 78.6% of the initial PL intensity, corresponding to the intensity of transition of Sm 3+ and transition of Tb 3+ in the Ba 3 NaLa 0.7 (PO 4 ) 3 F:0.10Tb 3+ ,0.20Sm 3+ phosphor, respectively. These results indicate the series of Ba 3 NaLa 1− x − y (PO 4 ) 3 F: x Tb 3+ , y Sm 3+ phosphors can be acted as a good candidate for the application in white light-emitting diodes. [ABSTRACT FROM AUTHOR]

BaLa2ZnO5:Er3+/Yb3+ has been synthesized via a high temperature solid-state method, and the tunable upconversion luminescence and energy transfer process between Yb3+ and Er3+ in this system have been demonstrated. Upon 980 nm laser excitation, the intense green and red emission around 527, 553, and 664 nm were observed for BaLa2ZnO5:Er3+/Yb3+, which can be assigned to the characteristic energy level transitions of 2H11/2 → 4I15/2, 4S3/2 → 4I15/2, and 4F9/2 → 4I15/2 of Er3+, respectively. The critical Er3+ quenching concentration (QC) was determined to be about 5 mol%, and the power studies indicated that mixture of 2- and 3-photon process was responsible for the green and red upconversion luminescence. [ABSTRACT FROM AUTHOR]

Eu 2+ –Tb 3+ co-doped Sr 3.5 Y 6.5 O 2 (PO 4 ) 1.5 (SiO 4 ) 4.5 (SYPSO) phosphors with apatite structure have been synthesized via a high temperature solid-state reaction and their luminescence properties have been investigated in detail. The two kinds of cations׳ sites and complex phosphate-silicate anions׳ structural character of SYPSO host have been studied. The SYPSO:Eu 2+ ,Tb 3+ phosphors show a broad absorption band ranging from 250 to 420 nm, which is well matched with the emission of near ultraviolet (UV) chips, and it exhibited two dominating bands peaked at 502 and 543 nm upon 365 nm excitation. The emission color of SYPSO:0.05Eu 2+ , y Tb 3+ shows a controlled luminescence evolution of the color hue in the green area owing to the Eu 2+ –Tb 3+ energy transfer (ET) process, and their chromaticity coordinates ( x , y ) can be varied from (0.2723, 0.3766) to (0.2812, 0.4537). The ET efficiency as well as the critical distance is also estimated. The quantum efficiency and thermal quenching properties have also been studied in this paper in order to demonstrate its potential application for white light-emitting diodes ( w -LEDs) phosphors. [ABSTRACT FROM AUTHOR]

The substituted activator ions Eu2+ in the β-Ca3(PO4)2-type structure, Ca9NaMg(PO4)7 compound, have been studied as emission centers, as well as structural probes. The crystal structure and crystallographic sites of Eu2+ in Ca9NaMg(PO4)7 have been identified by Rietveld refinements, electron paramagnetic resonance (EPR) spectroscopy analysis and combined photoluminescence spectral analysis, respectively. Ca9NaMg(PO4)7:Eu2+ phosphor exhibits a broad emission band in the visible light region with three distinguished peaks centered at 415, 458, and 615 nm, which are ascribed to different Eu2+ emission centers occupied in three different Ca crystallographic sites. The concentration quenching behavior, variation in lifetimes and the temperature dependent luminescence properties have been investigated as a function of different emission centers, 415, 458, and 625 nm for Ca9NaMg(PO4)7:Eu2+ phosphor. Accordingly, the relationship among three different Eu2+ luminescence centers originating from three different Ca2+ crystallographic sites has been found and verified. [ABSTRACT FROM AUTHOR]

Abstract: SiO2-coated Ca2BO3Cl:Eu2+ phosphors were prepared by the sol–gel method in order to enhance the chemical and thermal stabilities of Ca2BO3Cl:Eu2+ phosphor. The phase structures, microstructures and luminescence properties were studied by the X-ray diffraction (XRD), scanning electron microscopy (SEM) and fluorescence spectrometer, respectively. The emission intensity of SiO2-coated Ca2BO3Cl:Eu2+ phosphor decreased a little compared to that of the uncoated phosphor. The moisture resistances of the phosphors were comparatively examined by the aging treatment experiment in the water, and the thermal stability was studied by the temperature dependent photoluminescence spectra. The results indicated that SiO2 coating on the surface of the phosphor particles improved the moisture-resistance and thermal stability to a large extent. [Copyright &y& Elsevier]

A novel orange-red emitting orthosilicate phosphor LiGd 9 (SiO 4) 6 :Mn2+ (LGS:Mn2+) belongs to hexagonal lattice with P 6 3 / m space group was synthesized via solid-state method and the phase composition, crystal structure as well as luminescence properties were examined for potential application in near ultraviolet (n -UV) pumped white light emitting diodes (w -LEDs). The as-prepared LGS:Mn2+ phosphor exhibits three excitation bands peaked at 273, 312 and 410 nm, which corresponds to the transitions of Gd3+ from ground state 8S 7/2 to 6I 7/2 , 6P 7/2 and Mn2+ from ground state 6A 1 (6S) to the individual components of the multiplets [4A 1 (4G), 4E(4G)], respectively. Upon excitation at 312 nm, the phosphors display an intense broad orange-red emission peaked around 594 nm, which ascribed to the typical spin-forbidden transition (4T 1 (4G)-6A 1 (6S)) of the Mn2+ ions. The concentration quenching mechanism and average separation distance in conjunction with fluorescence decay times of Mn2+ ions in LGS:Mn2+ phosphor were discussed. The indispensable parameters for application in n -UV high-powered w -LEDs, such as the thermal quenching of photoluminescence and internal quantum efficiency of LGS:Mn2+ phosphor, have also been investigated in detail. The above results indicate that LGS:Mn2+ could play a key role as an orange-red emission for potential application in n -UV-based w -LEDs. • LiGd 9 (SiO 4) 6 O 2 :Mn2+ luminescent materials were synthesized successfully. • This phosphor have excellent thermal stability and emission efficiency. • High energy transfer efficiency could be obtained between Gd3+ and Mn2+ ions. [ABSTRACT FROM AUTHOR]

Abstract A single-component white-emitting phosphor Sr 9 La(PO 4) 5 (SiO 4)F 2 :Dy3+ pumped for n -UV-light emitting diodes was firstly presented by solid state method and the crystal structures, luminescence properties, especially the concentration quenching behaviors were discussed in detail. Accordingly, the quantum efficiencies as well as lifetime studies of Dy3+ in CLPGF phosphor were also carried out. The results revealed that the Sr 9 La(PO 4) 5 (SiO 4)F 2 :Dy3+ phosphor could be efficiently excited in a broad wavelength ranging near ultraviolet (n -UV) regions, which matched perfectly with n -UV white light emitting diodes (w -LEDs) chips. Under the excitation at 349 nm, the phosphor exhibited three prominent emission peaks in the visible wavelength region located at 483, 578 and 670 nm, which is ascribed to the 4F 9/2 -6H 15/2 , 4F 9/2 -6H 13/2 and 4F 9/2 -6H 11/2 transitions of Dy3+, respectively. It was also proved that the dipole-dipole interactions results in the concentration quenching in Sr 9 La(PO 4) 5 (SiO 4)F 2 :Dy3+ phosphors. Fascinatingly, when the temperature turned up to 150 °C, the emission intensity at 483 and 578 nm was 83.4 and 89.1% of the initial value at room temperature. Additional, the corresponding activation energy Δ E was determined to be 0.16999 and 0.17451 eV, which indicated the excellent thermal stability of the samples. All these findings demonstrated that as-prepared phosphors could act as a high-performance candidate for the application. Highlights • A single-component white-emitting phosphor has been successfully prepared. • As-prepared phosphor has good thermal stability and luminescence efficiency. • The structural data of Sr 9 La(PO 4) 5 (SiO 4)F 2 :Dy3+ is firstly reported. [ABSTRACT FROM AUTHOR]

Ca9La(PO4)5 (SiO4)F2:Dy3+ is prepared by solid state reaction of stoichiometric quantities of CaCO3, (NH4)2HPO4, SiO2, Dy2O3, and excess NH4HF2 as a flux ( 5% H2/N2 reducing atmosphere, alumina crucible, 1450 °C, 5 h). [ABSTRACT FROM AUTHOR]

The simple high-temperature solid-state route was adopted to synthesize a series of related Ba 3 LaK(PO 4 ) 3 F: x Eu 2+ (BLKPF: x Eu 2+ ) blue phosphors. The photoluminescence (PL) and diffuse reflection spectra have been investigated in detail. These phosphors which can be well excited by the 388 nm near ultraviolet light, produce the emitted blue light peaks located at about 460 nm. The critical Eu 2+ concentration quenching mechanism was ascribed to the dipole–dipole interaction, and the optimum concentration was eventually proved to be 0.1 mol. All above results indicate that Ba 3 LaK(PO 4 ) 3 F: x Eu 2+ phosphor can act as an appropriate candidate of the blue phosphor in the future. [ABSTRACT FROM AUTHOR]

A series of Dy3+-doped MGd 9 (SiO 4) 6 O 2 :Dy3+ (M = Li, Na, K) phosphors that generated white emission were prepared using the high temperature solid-state technique. Simultaneously, the phase composition, crystal structure, electronic structure, as well as the luminescence properties of the as-prepared phosphors were investigated in detail. The structural refinement showed that the MGd 9 (SiO 4) 6 O 2 crystallized with the hexagonal apatite-type structure. The unit cell parameters increased gradually and the main peaks of the samples in XRD patterns shifted towards high angles with the substitution of alkali-metal ions (from Li+ to K+). Under the excitation of 350 nm, the as-obtained MGd 9 (SiO 4) 6 O 2 :Dy3+ phosphors gave bright white emission with the major emission peaks centering at 454, 477 and 573 nm. And the R y/b , CIE chromaticity coordinate and the corrected color temperature (CCT) of the phosphors were adjusted from 0.96, (0.3256, 0.3625) and 4602 K to 1.13, (0.3369, 0.3582) and 4201 K attributing to the substitution in the crystal structure. The thermoluminescence study of MGd 8.90 (SiO 4) 6 O 2 :0.10Dy3+ (M = Li, Na, K) showed good stability and the decay lifetimes of the samples were estimated to be about 470 μs. All the results suggested that the luminescence properties could be modified by the substitution of alkali metal ions, and the MGd 9 (SiO 4) 6 O 2 :Dy3+ (M = Li, Na, K) phosphors have potential application as white emission candidate for w -LEDs. • Novel Dy3+ doped apatite structure phosphors were successfully synthesized. • The symmetrical environment could be modified to a certain extent owing to substitution of alkali metal ions. • The DFT calculation was used to check the electronic structure. [ABSTRACT FROM AUTHOR]

Ba 3 Sc(PO 4 ) 3 :Eu 2+ ,Tb 3+ (BSP:Eu 2+ ,Tb 3+ ) phosphors were successfully prepared via conventional high-temperature solid-state reaction, their luminescence properties as well as energy transfer mechanism have been investigated in detail. The energy transfer mechanism was proposed to be the dipole–quadrupole mechanism, and the energy transfer efficiency was also estimated. BSP:Eu 2+ ,Tb 3+ phosphors showed a broad emitting band centered at 518 nm and several sharp emission peaks, which were assigned to the 5 d →4 f allowed transitions of Eu 2+ ions and characteristic optical 5 D 4 – 7 F J ( J =6, 5, 4, and 3) transitions of Tb 3+ ions, respectively. The emission color of BSP:Eu 2+ , y Tb 3+ exhibited a controlled luminescence evolution in the green area owing to the Eu 2+ –Tb 3+ energy transfer process. [ABSTRACT FROM AUTHOR]

Er 3+ and/or Yb 3+ doped Sr 2 ScF 7 up-conversion (UC) phosphors were synthesized, and the optimum doping concentrations of Yb 3+ and Er 3+ in the Sr 2 ScF 7 host were found to be 20% mol and 7% mol, respectively. Under excitation of 980 nm laser, the UC spectra of the samples is composed of three green emission bands from 510 to 570 nm centered at 525, 543 and 551 nm and two red emission band from 640 to 690 nm with two peaks at 657 and 671 nm, which is attributed to the 2 H 11/2 , 4 S 3/2 → 4 I 15/2 and 4 F 9/2 → 4 I 15/2 transitions of Er 3+ , respectively. The UC emission color of Er 3+ can be tuned by adjusting the intensity ratio of red to green emission through manipulating the population of red and green emitting states. [ABSTRACT FROM AUTHOR]

SrAl 2 Si 2 O 8 : x Eu ( x = 0.5–8%) phosphors were prepared by the high-temperature solid-state reaction in air atmosphere. The phenomenon of Eu 2+ /Eu 3+ coexistence was observed and the color of the SrAl 2 Si 2 O 8 : x Eu phosphor could shift from light pink to blue by controllable and reproducible means. Photoluminescence (PL), excitation (PLE) spectra, X-ray photoelectron spectroscopy (XPS), and the fluorescence decay curves were employed to detect the presence of Eu 2+ and Eu 3+ ions in the compound. Under ultraviolet excitation, the broad band emission peaked at 410 nm originated from the transition of 4 f 6 5 d –4 f 7 from Eu 2+ and narrow band emissions peaked at 591 nm, 614 nm, 655 nm, and 703 nm are derived from the 4 f –4 f transition of Eu 3+ ions, although the Eu 3+ precursors were employed. The reduction mechanism from Eu 3+ to Eu 2+ in this compound was discussed in detail and verified by photoluminescence properties through changing the addition amount of Eu, temperature rise and holding time. [ABSTRACT FROM AUTHOR]

Highlights: [•] Novel Na0.60Ca0.40Sc0.60Mg0.40Si2O6:Eu2+,Mn2+ phosphors have been prepared. [•] Full-color white emission can be realized in the single host with different emission centers. [•] A white LED lamp was fabricated to demonstrate good luminescence properties. [ABSTRACT FROM AUTHOR]

Highlights: [•] Blue-emitting phosphor K2Ca2Si2O7:Ce3+ was synthesized. [•] The critical quenching concentration and concentration quenching mechanism was discussed. [•] Ce3+ emission centre in K2Ca2Si2O7 were studied by the photoluminescence spectra and decay curves. [ABSTRACT FROM AUTHOR]

Highlights: [•] Ca10(PO4)6F2:Bi3+, Eu3+ phosphors have been synthesized. [•] Energy transfer happens from Bi3+ to Eu3+ with an optimum efficiency of 50.3%. [•] The energy transfer mechanism has been discussed. [ABSTRACT FROM AUTHOR]

Ce3+ doped K 3 LuF 6 powders have been successfully elaborated via high-temperature solid state method. The structural and luminescent properties of these cryolite-type K 3 LuF 6 : x Ce3+ (x = 0.03, 0.05, 0.07, 0.10 and 0.13) phosphors have been investigated into detail. The results indicate that all phases belong to the monoclinic system with P2 1 /n space group and lattice parameters a = 6.295 (4) Å, b = 6.497 (5) Å, c = 8.992 (6) Å, β = 90.91 (3) ° for x = 0.05. Ce3+ is considered to substitute for Lu3+ in the octahedral [LuF 6 ] sites. Under UV light excitation at 307 nm, the photoluminescence spectra of the samples present one broad band centered around 432 nm which belongs to the purplish-blue region. The color coordinates of this phase are calculated to (0.1565, 0.0956). The influence of Ce3+ content on the luminescence properties is also established and the concentration quenching mechanism is due to dipole-quadrupole Ce3+-Ce3+ interactions in K 3 LuF 6 :Ce3+. Rietveld refinement of XRD pattern and crystal structure of K 3 LuF 6 :0.05Ce3+ (left); The PL spectra of K 3 LuF 6 :xCe3+ (x = 0.03, 0.05, 0.07, 0.10, and 0.13) monitored by excitation at 307 nm and the inset is dependence of PL intensity on the Ce3+ doping content (right). Image 1 [ABSTRACT FROM AUTHOR]

Samarium (III) doped fluorapatite phosphors La 6- x Ba 4 (SiO 4 ) 6 F 2 : x Sm 3+ (LBSF: Sm 3+ ) were synthesized for the first time, via the conventional high-temperature solid-state method in the air atmosphere. The samples were measured by X-ray diffraction, scanning electron microscopy and photoluminescence spectroscopy, i.e. emission and excitation spectra, as well as luminescence decay curves. The as-prepared samples can be excited in the range from 300–500 nm, centered at 404 nm. Photoluminescence measurements showed the emission spectra are composed of four sharp peaks characteristic of Sm 3+ ions, at about 565, 603, 650 and 711 nm. The critical concentration for quenching of Sm 3+ ions in the LBSF matrix is about 0.12 mol. According to the Dexter's theory, the mechanism of energy transfer between Sm 3+ ions was considered to be dipole-quadrupole (d-q) interactions, with the critical distance calculated by the concentration quenching method to 9.89 Å. Moreover, the temperature-dependent emission spectra showed that the as-prepared phosphors have good thermal stability, with an activation energy of about 0.161 eV. Finally, according to the CIE coordination, the phosphor exhibited reddish-orange emission. Thanks to the mentioned favorable structural and optical properties, the Sm 3+ -doped La 6 Ba 4 (SiO 4 ) 6 F 2 phosphors have a potential application character, for the near ultraviolet white light emitting diodes. [ABSTRACT FROM AUTHOR]

Upconversion phosphors Sr 2 LaF 7 co-doped with Yb 3+ and Er 3+ are synthesized via hydrothermal method. The phase compositions of Sr 2 LaF 7 phosphors with different amounts of Yb 3+ and Er 3+ dopants, pH values, and complexing agents are characterized by X-ray diffraction (XRD). The crystal structure and morphology of Sr 2 LaF 7 phosphor doped with 15% Yb 3+ / 1% Er 3+ is refined by the Rietveld method and transmission electron microscopy (TEM). Under 980 nm laser excitation, Yb 3+ and Er 3+ co-doped Sr 2 LaF 7 phosphors exhibit red emission around 670 nm generated by the 4 F 9/2 → 4 I 15/2 transition and green emissions centering around 550 nm and 523 nm generated by the 4 S 3/2 → 4 I 15/2 and 2 H 11/2 → 4 I 15/2 transitions of Er 3+ , respectively. The optimum synthetic conditions for upconversion luminescence for Sr 2 LaF 7 co-doped with Yb 3+ and Er 3+ are discussed and determined to be 15% Yb 3+ / 1% Er 3+ with EDTA-2Na as the complexing agent under pH value = 8, and the corresponding Commission International de L′Eclairage (CIE) coordinates are calculated to be x  = 0.4293 and y  = 0.5589 with reddish yellow color visible to naked eyes under the 980 nm laser excitation. The related upconversion mechanisms of Yb 3+ and Er 3+ co-doped Sr 2 LaF 7 depending on the pump power are also studied in detail. [ABSTRACT FROM AUTHOR]

In this paper, a series of novel luminescent Sr 10− x (SiO 4 ) 3 (SO 4 ) 3 O: x Eu 2+ phosphors with apatite structure were synthesized by a high temperature solid-state reaction. The phase structure, photoluminescence (PL) properties, as well as the PL thermal stability were investigated. Sr 9.92 (SiO 4 ) 3 (SO 4 ) 3 O:0.08Eu 2+ phosphor exhibits better thermal quenching resistance, retaining the luminance of 66.55% at 150 °C compared with that at 25 °C. The quenching concentration of Eu 2+ in Sr 10 (SiO 4 ) 3 (SO 4 ) 3 O was about 0.08 (mol) with the dipole–quadrupole interaction. The Sr 10− x (SiO 4 ) 3 (SO 4 ) 3 O: x Eu 2+ phosphors exhibited a broad-band green emission at 538 nm upon excitation at 396 nm. The results indicate that Sr 10− x (SiO 4 ) 3 (SO 4 ) 3 O: x Eu 2+ phosphors have potential applications as near UV-convertible phosphors for white-light UV LEDs. [ABSTRACT FROM AUTHOR]

A series of blue-emitting La 5.90− x Ba 4+ x (SiO 4 ) 6− x (PO 4 ) x F 2 :0.10Ce 3+ ( x = 0, 1, 2, and 3) phosphors with apatite structure were synthesized by a solid-state reaction. The crystal structure and the photoluminescence properties were investigated in detail. The crystallographic occupancy of Ce 3+ in La 2.90 Ce 0.10 Ba 7 (SiO 4 ) 3 (PO 4 ) 3 F 2 and La 5.90 Ce 0.10 Ba 4 (SiO 4 ) 6 F 2 were studied based on Rietveld refinements results and the crystal chemistry rules. La 5.90− x Ba 4+ x (SiO 4 ) 6− x (PO 4 ) x F 2 :0.10Ce 3+ exhibited strong blue light emission in the range of 407–414 nm with high thermal stability upon excitation at 276 nm. Besides, the activation energy E of La 5.90 Ce 0.10 Ba 4 (SiO 4 ) 6 F 2 and La 2.90 Ce 0.10 Ba 7 (SiO 4 ) 3 (PO 4 ) 3 F 2 phosphors were calculated to be 0.152 and 0.177 eV. These results suggest that La 5.90− x Ba 4+ x (SiO 4 ) 6− x (PO 4 ) x F 2 :0.10Ce 3+ is a potential blue phosphor candidate for near-UV-pumped w -LEDs. [ABSTRACT FROM AUTHOR]

Single-phase La 6 Sr 4 (SiO 4 ) 6 F 2 : Ce 3+ , Tb 3+ samples with apatite-like structure have been synthesized via solid-state reaction method. The phase structure, luminescence properties, lifetime, the PL thermal stability, as well as the fluorescence decay curves of the samples were investigated to characterize the resulting samples. Effective energy transfer occurs from Ce 3+ to Tb 3+ in La 6 Sr 4 (SiO 4 ) 6 F 2 , which shows more intense Blue-Green light under UV light excitation. In addition, a possible mechanism of the energy-transfer from Ce 3+ to Tb 3+ ion is also proposed. The critical distance R C of Ce 3+ to Tb 3+ ions in La 6 Sr 4 (SiO 4 ) 6 F 2 host was calculated to be 11.878 Å. All the results indicate that La 6 Sr 4 (SiO 4 ) 6 F 2 :Ce 3+ , Tb 3+ phosphors have potential applications to be used as near UV-convertible phosphors for white light-emitting diodes. [ABSTRACT FROM AUTHOR]

Tm 3+ /Yb 3+ co-doped BaLa 2 ZnO 5 up-conversion (UC) phosphors were successfully synthesized by high temperature solid-state reaction method. The X-ray diffraction (XRD) results show that synthesized phosphor co-doped with 0.75% Tm/10% Yb has the optimum pure phase of BaLa 2 ZnO 5 among different co-doping concentrations. The structure of BaLa 2 ZnO 5 :0.75% Tm/10% Yb phosphor was refined by the Rietveld method and results show the decreased unit cell parameters and cell volume after doping Tm 3+ /Yb 3+ , indicating that Tm 3+ /Yb 3+ have successfully replaced La 3+ . Under excitation at 980 nm, Tm 3+ /Yb 3+ co-doped BaLa 2 ZnO 5 phosphors present bright blue emission near 478 nm generated by the 1 G 4 → 3 H 6 transition and weak red emissions around 653 nm and 692 nm generated by the 1 G 4 → 3 F 4 and 3 F 3 → 3 H 6 transitions of Tm 3+ , respectively. The UC luminescence properties of BaLa 2 ZnO 5 phosphors co-doped with different Tm 3+ /Yb 3+ concentrations were investigated, and the related UC mechanisms of Tm 3+ /Yb 3+ co-doped BaLa 2 ZnO 5 depending on pump power were studied in detail. [ABSTRACT FROM AUTHOR]

A series of new luminescent emission-tunable phosphors Sr 2 La 8 (SiO 4 ) 6 O 2 :Ce 3+ , Tb 3+ with apatite structure have been synthesized by a high temperature solid-state reaction. The phase structure, photoluminescence emission and excitation spectra, lifetime, as well as the effect of Tb 3+ concentration are investigated to characterize the resulting samples. The critical distance was calculated to be 8.26 Å by using the concentration quenching method. The intense green emission was observed in the Sr 2 La 8 (SiO 4 ) 6 O 2 :Ce 3+ , Tb 3+ phosphors on the basis of the efficient energy transfer from Ce 3+ to Tb 3+ with an efficiency of 68.55%. And a possible mechanism of the energy-transfer from Ce 3+ to Tb 3+ ion is also proposed. The results indicate that Sr 2 La 8 (SiO 4 ) 6 O 2 :Ce 3+ , Tb 3+ phosphors have potential applications to be used as near UV-convertible phosphors for white light-emitting diodes because of the broad excitation in the near-ultraviolet range and the efficient green emission light. [ABSTRACT FROM AUTHOR]

In this paper, K 3 ScF 6 :Er3+,Yb3+ up-conversion luminescent materials with cryolite structure were synthesized via solid-state method. The X-ray diffraction (XRD), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS) and photoluminescence spectroscopy (PL) under the excitation of a 980 nm laser with different power density were used to investigate the phase structure, elemental composition, and up-conversion luminescence properties of K 3 ScF 6 :Er3+,Yb3+. The quenching concentrations of Yb3+ and Er3+ were confirmed to 0.15 and 0.05 (mol concentration) in this system, respectively. Upon 980 nm excitation, the K 3 ScF 6 :Er3+,Yb3+ showed a typical transition of Er3+ which contains two main bands in the visible region that green and red. According to the fitting result of the pump power dependence of up-conversion intensity, all the green and red up-conversion emission of K 3 ScF 6 :0.05Er3+,0.15 Yb3+ belong to the two-photon process. To better understand the origin of radiation and energy transfer mechanism of the red and green up-conversion, the possible mechanism and electron transition process were also discussed. Single-phase Er3+/Yb3+ co-doped K 3 ScF 6 with cryolite structure were synthesized. Image 1 • Single-phase Er3+/Yb3+ co-doped K 3 ScF 6 with cryolite structure was synthesized. • Structural and up-conversion properties of K 3 ScF 6 :Er3+, Yb3+ were studied. • Mechanism of up-conversion was analyzed. [ABSTRACT FROM AUTHOR]

In this paper, K 3 ScF 6 :Yb3+, Tm3+ phosphor with a cubic cryolite phase were prepared by means of high-temperature solid-state method. The crystal structure and up-conversion luminescence properties of Tm3+ and Yb3+ co-doped K 3 ScF 6 were investigated in detail. Scanning electron microscope (SEM), energy disperse spectroscopy (EDS), elemental mapping and X-ray photoelectron spectroscopy (XPS) were used to analyze the elements composition, elemental distribution and valence states of samples. Under an excitation wavelength at 980 nm, all the samples displayed blue and red emission. When gradually increasing the concentration of Tm3+ in K 3 ScF 6 :0.2 Yb3+, Tm3+ and Yb3+ in K 3 ScF 6 : 0.01 Tm3+, Yb3+, the emission intensity of the samples appeared obviously concentration quenching effect, and the optimum concentration of Tm3+ and Yb3+ were confirmed to 0.01 and 0.20 mol%. Additionally, the effect of pump power on up-conversion emission intensity and the energy transfer mechanism between the Tm3+ and Yb3+ in these samples were analyzed in detail. • Single-phase Tm3+/Yb3+ co-doped K 3 ScF 6 with cryolite structure were synthesized for the first time. • Up-conversion properties of K 3 ScF 6 : Yb3+, Tm3+ were studied. • Mechanism of up-conversion was analyzed. [ABSTRACT FROM AUTHOR]

A new kind of multicolor phosphor Ba 2 La 3 (SiO 4) 3 Cl:0.15Tb3+, x Eu3+ (BLSOCl:0.15Tb3+, x Eu3+) has been acquired through the traditional high temperature solid phase synthesis method. The structure information of the phosphor was studied by X-ray diffraction (XRD), scanning electron microscopy (SEM) and Rietveld refinement. The optical properties of the phosphor have also been studied in detail, including photoluminescence spectra (PL), photoluminescence excitation spectra (PLE), fluorescence decay curves, energy transfer mechanism and thermal quenching spectra. The CIE values have also been studied. All the properties are good and can contribute to the promotion from the laboratory to practical application for the phosphor. Image 1 [ABSTRACT FROM AUTHOR]

Single-phase Ba10-x-y (PO4)6O:xEu2+,yMn2+ phosphors are prepared by solid state reaction of stoichiometric mixtures of BaCO3, NH4H2PO4, Eu2O3, and MnCO3 (alumina crucibles, flowing 10% H2/90% N2, 1200 °C, 5 h). [ABSTRACT FROM AUTHOR]

Sr10(PO4)6O:Eu2+x (x = 0.005-0.07) is prepared by solid state reaction of stoichiometric amounts of SrCO3, (NH4)2HPO4, and Eu2O3 in a reducing atmosphere of 5% H2/N2 (alumina crucible, 1300 °C). [ABSTRACT FROM AUTHOR]

The title phosphors are prepared by solid state reactions of SrCO3, SiO2, CeO2, La2O3, and Tb4O7 (alumina crucible, flowing 5%H2/95%N2, 1350 °C, 5 h). [ABSTRACT FROM AUTHOR]