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Following the rapid growth of lightning technology, the development of red-emitting phosphors is effective for improving color temperature and color rendering index for w-LEDs devices. Herein, a single phased garnet phosphor with cation and polyhedron substitution modification was firstly prepared. For Mg 3 Gd 2 Ge 3 O 12 : Bi3+, Eu3+, the intensity has been remarkably improved by about 16% compared to the one without Bi3+ sensitization. The energy transfer mechanism is identified in this work. Based on cation and polyhedron substitution strategies, novel phosphors with different compositions were obtained and further modified the PL properties. With Lu3+ substitution, the bond lengths between Bi3+ ion and anion ligands are decreased and the site symmetry has been strengthened, which leads to a 21 nm blue shift when Lu3+ totally replaced Gd3+ ions. In addition, Lu3+ and [SiO 4 ] substitution strategies both effectively increased symmetric rigid structure, which leads to a significant improvement in thermal stability, indicating the samples own great potential in optical applications This work provides a new insight to synthesis red-emitting phosphors for warm white-LEDs. [ABSTRACT FROM AUTHOR]

A novel apatite structure phosphor Ca 9 La(PO 4 ) 5 (GeO 4 )F 2 :Dy 3+ (CLPGF:Dy 3+ ) with a hexagonal lattice in the P 6 3 / m space group was synthesized via a facile solid state technique. The crystal and fine local structure as well as their photoluminescence properties were investigated in detail. The CLPGF:Dy 3+ phosphor can absorb in the UV-vis spectral region of 290–475 nm and exhibit two intense emission bands centered at 485 and 580 nm, which ascribes to 4 F 9/2 → 6 H 15/2 and 4 F 9/2 → 6 H 13/2 transitions of Dy 3+ , respectively. The concentration quenching of Dy 3+ emission occurs via the energy transfer among the nearest-neighbor ions and the corresponding quenching mechanism was verified to be the dipole-dipole interaction. The quantum efficiencies of the phosphors were examined to be 72.9% and its luminescence intensity at 150 °C decreases to 93.8% and 98.6% of the initial value at room temperature, which corresponds to 4 F 9/2 to 6 H 15/2 transition and 4 F 9/2 to 6 H 13/2 transition of Dy 3+ ions, respectively. Their interesting photoluminescence properties indicate that the CLPGF:Dy 3+ phosphor is a promising white-emitting candidate for w -LEDs applications. [ABSTRACT FROM AUTHOR]

Novel reddish Mg 3 Gd 2 Ge 3 O 12 : RE3+ (RE = Sm, Eu) phosphors with high thermal stability have been designed and developed. In this work, Mg 3 Gd 2 Ge 3 O 12 was first synthesized for being used as the phosphor host. The X-ray diffraction and Rietveld refinement testified that the MGGO: Sm3+ and MGGO: Eu3+ crystallized in a cubic unit cell with space group I a-3d (230). The photoluminescence properties were studied in detail, MGGO: Sm3+ and MGGO: Eu3+ can be obviously excited at 403 and 395 nm, which could guarantee efficient absorption through commercial n -UV chip. Benefiting from the inverse garnet highly rigid framework, MGGO: 0.04Sm3+ and MGGO: 0.9Eu3+ phosphors had a favorable thermal resistance due to large activation energies (MGGO: 0.04Sm3+: 0.291 eV, MGGO: 0.9Eu3+: 0.238 eV). The emission intensity of MGGO: 0.04Sm3+ and MGGO: 0.9Eu3+ can still preserve about 97.85% and 91.58% at working temperature (423 K) compared to the initial intensity (298 K). All results indicated Mg 3 Gd 2 Ge 3 O 12 : RE3+ (RE = Sm, Eu) phosphors have potential usage for full-spectrum w-LED applications as red component. • Crystal structure of MGGO: 0.04Sm3+ and MGGO: 0.9Eu3+ phosphors are investigated in detail. • MGGO: 0.04Sm3+ and MGGO: 0.9Eu3+ phosphors have a favorable thermal resistance due to large activation energies. • MGGO: 0.04Sm3+ and MGGO: 0.9Eu3+ can be obviously excited at 403 and 395 nm. • CIE chromaticity coordinates of MGGO: 0.04Sm3+ and MGGO: 0.9Eu3+ are (0.5153, 0.4709) and (0.4937, 0.3765). [ABSTRACT FROM AUTHOR]

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 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]

In this study, La 2 (MoO 4) 3 doped with Eu3+ was synthesized by the high-temperature solid-state method. The phase composition of the Eu3+-doped La 2 (MoO 4) 3 sample was confirmed by X-ray powder diffraction (XRD) analysis, and the microstructure was observed via the scanning electron microscopy (SEM). Under the excitation at 211 nm, the room temperature emission spectra of Eu3+ in the samples with different doping levels were recorded. In addition, the prepared La 2 (MoO 4) 3 : x Eu3+ (x = 0–0.25) phosphors were color tunable. A non-contact optical thermometer with high sensitivity and high-temperature resolution was fabricated based on the different thermal quenching behaviors of the Mo–O group and Eu3+ center. The fluorescence intensity ratio (FIR), temperature resolution (ΔT), maximum absolute and relative sensor sensitivity (Sa and Sr) of La 2 (MoO 4) 3 :Eu3+ were calculated according to different thermal quenching effects between room temperature (298K) and 573K of Eu3+ and Mo–O group. These results show that La 2 (MoO 4) 3 :Eu3+ has excellent sensitivity and temperature resolution, good reversibility and reliability, as Sa = 0.0525 K-1, Sr = 0.3724. % K−1, ΔT = 0.0806 K and the FIR error was only 0.62%. Therefore, the Eu3+-doped La 2 (MoO 4) 3 is a promising candidate material for high performance non-contact optical thermometers. [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]

A series of novel Na 3 Ga (1- x ) F 6 : x Eu 3+ ( x  = 1%, 3%, 5%, 7% and 10%) phosphors were synthesized by hydrothermal synthesis method. The crystal structure and luminescence properties of Na 3 GaF 6 :Eu 3+ were characterized by X-ray powder diffraction (XRD), Scanning electron microscope (SEM), photoluminescence (PL) and photoluminescent excitation spectra (PLE) as well as decay curves. The results indicated that Eu 3+ can replace Ga 3+ in the lattice of Na 3 GaF 6 without any impurity. The micro-particle of the phosphor was uniform and regular with a smooth surface. Upon 395 nm excitation, the phosphors show intense reddish-orange color including a series of narrow peaks attributed to the typical f–f transition of Eu 3+ . Not like most of other rare-earth doped sample, the Na 3 GaF 6 :Eu 3+ phosphors show obvious anti-thermal quenching behavior. All the results demonstrated that Na 3 GaF 6 :Eu 3+ phosphors exhibit good luminescent properties and might have a potential to applications in lighting technology. [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]

In this paper, Ce 3+ -activated iso-structural solid solutions La 5.99 Ce 0.01 M 4 (SiO 4 ) 6 F 2 (M = Ca, Sr and Ba) compounds were prepared for the first time. The structure and luminescence properties of the samples were investigated to explore the difference of cation substitution. The phase analysis indicated that all XRD peaks of the samples were indexed by a hexagonal cell with the space group of P 6 3 /m, and the phosphors showed strong blue light emission with broad bands. With the isomorphous substitution of Ba → Sr → Ca, the average bond length between Ce 3+ and anions is decreased and the crystal field around Ce 3+ is strengthened, resulting in the red-shift (from 410 nm to 423 nm) of the emission wavelength for La 5.99 Ce 0.01 M 4 (SiO 4 ) 6 F 2 (M = Ca, Sr, Ba). [ABSTRACT FROM AUTHOR]

A series of yellow-emitting oxynitride Ca 0.65 Si 10 Al 2 O 0.7 N 15.3 : x Eu 2+ phosphors with α-sialon structure were synthesized. The phase composition and crystal structure were identified by X-ray diffraction and the Rietveld refinement. The excitation and emission spectra, reflectance spectra and thermal stability were investigated in detail, respectively. Results show that Ca 0.65 Si 10 Al 2 O 0.7 N 15.3 :0.12Eu 2+ phosphors can be efficiently excited by UV-Vis light in the broad range of 290–450 nm and exhibit broad emission spectra peaking at 550–575 nm. The concentration quenching mechanism are discussed in detail and determined to be the dipole-dipole interaction. When the temperature increased to 150 °C, the emission intensity of Ca 0.65 Si 10 Al 2 O 0.7 N 15.3 :0.12Eu 2+ phosphor is 88.46% of the initial value at room temperature. White LED was fabricated with N-UV LED chip combined with blue Ca 3 Si 2 O 4 N 2 :Ce 3+ and yellow Ca 0.65 Si 10 Al 2 O 0.7 N 15.3 :Eu 2+ phosphors. The color rendering index and correlated color temperature of this white LED were measured to 78.94 and 6728.12 K, respectively. All above results demonstrate that the as-prepared Ca 0.65 Si 10 Al 2 O 0.7 N 15.3 : x Eu 2+ may serve as a potential yellow phosphor for N-UV w-LEDs. [ABSTRACT FROM AUTHOR]

The Ca 9 La(PO 4 ) 5 (SiO 4 )Cl 2 :Dy 3+ (CLPSCl:Dy 3+ ) powder phosphor with apatite structure has been successfully synthesized via high-temperature solid state method. Single phase in such phosphor was verified through X-ray diffraction (XRD) technique. The Dy ions concentration dependent luminescence properties including emission, excitation and lifetimes of Dy ions were characterized using photoluminescence (PL) spectroscopy. The results showed that CLPSCl:Dy 3+ phosphor could efficiently assimilate the n -UV light and emit blue (~486 nm) and yellow light (~578 nm), originating from the f-f transitions of Dy 3+ . The critical Dy 3+ quenching concentration (QC) was determined to be about 12 mol%. The concentration quenching mechanism was also determined to be dipole–dipole interaction. [ABSTRACT FROM AUTHOR]

Tb 3+ -Sm 3+ co-doped Sr 9 Gd(PO 4 ) 5 (SiO 4 )F 2 (SGPSF) phosphors were prepared through a solid-state reaction, and their luminescence properties as well as energy transfer mechanism have been investigated in detail. The SGPSF:Tb 3+ , Sm 3+ phosphors system could be efficiently excited at wavelengths ranging from 200 to 500 nm, which is well matched with the spectra of near ultraviolet chips. The emission of SGPSF:Tb 3+ , Sm 3+ phosphor covers the entire visible region with sharp peaks in the blue, green, and red regions. The emission color of SGPSF:Tb 3+ , Sm 3+ could be adjusted from green (0.275, 0.378) to red (0.519, 0.295) by controlling the doping content of Sm 3+ /Tb 3+ . [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]

In this paper, a series of novel luminescent Sr 1− x Al 12 O 19 : x Eu 2+ phosphors were synthesized by a high temperature solid-state reaction. The phase structure, photoluminescence (PL) properties, as well as the decay curves were investigated. The quenching concentration of Eu 2+ in SrAl 12 O 19 was about 0.15 (mol). Upon excitation at 378 nm, the composition-optimized Sr 0.85 Al 12 O 19 :0.15Eu 2+ exhibited strong broad-band green emission at 530 nm with the CIE chromaticity (0.2917, 0.5736). The results indicate that Sr 1− x Al 12 O 19 : x Eu 2+ phosphors have potential applications as green-emitting phosphors for UV-pumped white-light LEDs. [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]

A series of Eu 2+ and Eu 2+ /Tb 3+ co-doped Ba 3 GdNa(PO 4 ) 3 F phosphors have been synthesized via a high temperature solid-state reaction. The relative intensity of PL spectra of Ba 3 GdNa(PO 4 ) 3 F: x Eu 2+ increases with increasing x value, and reaches a maximum at x =0.04. Ba 3 GdNa(PO 4 ) 3 F:Eu 2+ , Tb 3+ phosphors exhibit a broad excitation band ranging from 220 to 450 nm, which matches perfectly with the characteristic emission of n -UV light-emitting diode (LED) chips. Upon 365 nm excitation, the Ba 3 GdNa(PO 4 ) 3 F:Eu 2+ , Tb 3+ phosphors show two dominating bands peaked at 466 and 543 nm, which are assigned to the 4f 7 →4f 6 5d 1 transition of the Eu 2+ ions and the 5 D 4 → 7 F 5 transition of the Tb 3+ ions, respectively. In view of the energy transfer mechanism between Eu 2+ and Tb 3+ , the Ba 3 GdNa(PO 4 ) 3 F:Eu 2+ , Tb 3+ emission color can adjust from blue to green, and their chromatic coordinates ( x , y ) vary from (0.16, 0.135) to (0.254, 0.398). The critical distance was also calculated to be 16.90 Å. The above results indicate that the Ba 3 GdNa(PO 4 ) 3 F: Eu 2+ , Tb 3+ phosphors are a candidate for blue–green components in the application of n -UV w -LEDs. [ABSTRACT FROM AUTHOR]