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Abstract: Adjusting the elemental composition of a host is regarded to be an effective strategy to tune its luminescent properties such as peak energy, emission efficiency, and bandwidth. In this work, the cation substitution of (Ba2+ → Sr2+) in self‐activated Sr6V2O11 was conducted to investigate the luminescence modification. All the phosphors of Sr6‐6xBa6xV2O11 (x = 0, 0.1, 0.2, 0.3, 0.4, 0.5) were synthesized by the traditional chemical sol‐gel method. The morphological properties were measured through scanning electron microscope and energy dispersive spectrum measurements. The cation substitution brings out the disorder in the structure, which exerts modifications on the luminescence properties of Sr6V2O11. The luminescence intensity and corresponding decay lifetime were enhanced with the cation disorder in the self‐activated phosphor. Cation disorder in a phosphor lattice could be one of the effective approaches to improve the luminescence efficiency. [ABSTRACT FROM AUTHOR]

Abstract: Adjusting the elemental composition of a host is regarded to be an effective strategy to tune its luminescent properties such as peak energy, emission efficiency, and bandwidth. In this work, the cation substitution of (Ba2+ → Sr2+) in self‐activated Sr6V2O11 was conducted to investigate the luminescence modification. All the phosphors of Sr6‐6xBa6xV2O11 (x = 0, 0.1, 0.2, 0.3, 0.4, 0.5) were synthesized by the traditional chemical sol‐gel method. The morphological properties were measured through scanning electron microscope and energy dispersive spectrum measurements. The cation substitution brings out the disorder in the structure, which exerts modifications on the luminescence properties of Sr6V2O11. The luminescence intensity and corresponding decay lifetime were enhanced with the cation disorder in the self‐activated phosphor. Cation disorder in a phosphor lattice could be one of the effective approaches to improve the luminescence efficiency. [ABSTRACT FROM AUTHOR]

Red-emitting phosphor of Eu 3+ -activated BaY 6 (Si 3 B 6 O 24 )F 2 was synthesized by high-temperature solid state reaction. The phase purity was characterized by X-ray powder diffraction. Luminescent properties were characterized by photoluminescence excitation (PLE) and emission (PL) spectra, decay curves, and absolute quantum efficiency. The optimal doping concentration of Eu 3+ in BaY 6 (Si 3 B 6 O 24 )F 2 : is about 30 mol%. This phosphor can be efficiently excited by near-ultraviolet light to realize reddish-orange color from the dominated 5 D 0 → 7 F 1 transition. In addition, the thermal stability was investigated according to the temperature-dependent PL spectra. Eu 3+ -doped BaY 6 (Si 3 B 6 O 24 )F 2 has higher brightness and thermal stability, and shows a great potential for its application in LEDs as a suitable red-emitting phosphor. [ABSTRACT FROM AUTHOR]

Eu2+-doped zinc fluoro-phosphate Zn2[ PO4] F was synthesized by the conventional high-temperature solid-state reaction. The phase formation was confirmed by X-ray powder diffraction measurements and the structure refinement. The photoluminescence excitation and emission spectra, and the decay curves were measured. The natures of the Eu2+ emission in inorganic hosts, e.g., the emission and excitation properties, the chromaticity coordinates, the Stokes shifts, the absolute quantum efficiency, and the luminescence thermal stability were reported. Under the excitation of near- UV light, Eu2+-doped Zn2[ PO4] F presents a narrow blue-emitting band centered at 423 nm. The thermal stability of the blue luminescence was evaluated by the luminescence intensities as a function of temperature. The phosphor shows an excellent thermal stability on temperature quenching effects. [ABSTRACT FROM AUTHOR]

Eu/Mn-doped KCaPO phosphors were prepared by conventional solid-state reaction. X-ray powder diffraction (XRD), SEM, photoluminescence excitation, and emission spectra, and the luminescence decay curves were measured. Mn singly doped KCaPO shows the weak origin-red luminescence band peaked at about 590 nm. The Eu/Mn co-doped phosphors emit two distinctive luminescence bands: a blue one centered at 480 nm originating from Eu ions and a broad red-emitting one peaked at 590 nm from Mn ions. The luminescence intensity from Mn ions can be greatly enhanced with the co-doping of Eu ions. The efficient energy transfer from Eu to Mn was verified by the photoluminescence spectra together with the luminescence decay curves. The resonance-type energy transfer via a dipole-quadrupole interaction mechanism was supported by the decay lifetimes. The emission colors could be tuned by changing the Mn-doping concentration. [ABSTRACT FROM AUTHOR]

Highlights: [•] Green-origin-emitting phosphors of Eu2+-doped Ca7Si2P2O16 were firstly prepared by chemical sol–gel method. [•] The tunable luminescence color was realized by the changing Eu2+-doping in Ca7Si2P2O16. [•] Ca7Si2P2O16:Eu2+ displays two typical luminescence centers with the emission depending on Eu2+ doping. [•] Eu2+-doped Ca7Si2P2O16 phosphor has an excellent thermal stability on the temperature quenching. [ABSTRACT FROM AUTHOR]

A novel red-emitting nano-phosphor of Eu-doped GdMoO was successfully synthesized by the Pechini method. The crystalline phase was confirmed by X-ray powder diffraction analysis. The morphology of the nano-phosphor was analyzed by scanning electron microscopy, indicating a good crystallization with particles smaller than 500 nm. The luminescence properties such as photoluminescence spectra and decay curves were investigated. The phosphors can be efficiently excited by near-ultraviolet (near-UV) light and exhibit a bright red luminescence around 613 nm ascribed to the forced electric dipole transition D→F of Eu ions. The thermal stabilities were investigated from the temperature-dependent luminescence decay curves (lifetimes) and spectra intensities. The luminescence properties in relation to applications in white light-emitting diodes (W-LEDs) such as the absolute luminescence quantum efficiency, excitation wavelength, and color coordinates were discussed. The GdMoO:Eu nano-phosphor is a promising red-emitting candidate for the fabrication of W-LEDs with near-UV chips. [ABSTRACT FROM AUTHOR]

Abstract: A series of Ce3+, Tb3+ singly doped and Ce3+ /Tb3+-co-doped Mg2La3[SiO4]2[PO4]O phosphors with the apatite-like structure were prepared by conventional solid-state reaction. The X-ray diffraction (XRD), photoluminescence excitation and emission spectra, luminescence decay curves and lifetimes were applied to characterize the samples. The efficient excitation energy transfer from Ce3+ to Tb3+ was verified by the excitation and emission spectra together with the luminescence decay curves. The Ce3+/Tb3+ co-doped phosphor shows an intense broad excitation band between 300 and 430nm, which matches near-UV chip (350–420nm). Under the excitation of near UV light, the Ce3+/Tb3+ co-doped sample exhibits two distinct luminescence bands: a blue one centered at about 415nm originating from Ce3+ ions and a green-emitting at 543nm from the 5D4→7F5 transition of Tb3+ ions. The emission can be tuned from the blue to the green color by changing the doping concentration of Tb3+. The energy transfer from Ce3+ to Tb3+ has been demonstrated to be the dipole–quadrupole mechanism, and the critical distance is calculated to be 16.04Å. [Copyright &y& Elsevier]

The new red-emitting phosphors of Eu3+-doped triple orthovanadates Na A La( VO4)2 ( A = Ca, Sr, Ba) were prepared by the high-temperature solid-state reaction. The formation of single phase compound with isostructural structure of Ba3( VO4)2 was verified through X-ray diffraction ( XRD) studies. The photoluminescence excitation and emission spectra, the fluorescence decay curves and the dependence of luminescence intensity on doping level were investigated. The phosphor can be efficiently excited by near UV and blue light to realize an intense red luminescence (613 nm) corresponding to the electric dipole transition 5D0→7F2 of Eu3+ ions. Their potential applications as red-emitting phosphors for solid-state lighting were evaluated in comparison with the Eu3+-doped lanthanum orthovanadate LaVO4 and other reported references. The luminescence was discussed in detail on the base of the crystal structures. The luminescence thermal stability on temperature was investigated and the thermal activated energy was calculated. The phosphors can be suggested to be a potential red-emitting phosphor for the application on white LEDs under irradiation of near- UV or blue chips. [ABSTRACT FROM AUTHOR]

Abstract: A series of red-emitting phosphors of MR2(MoO4)4:Eu3+ (M=Ba, Sr, Ca; R=La3+, Gd3+, Y3+) were prepared by solid-state reaction. The photoluminescence excitation and emission spectra were investigated. The phosphors can be efficiently excited by the near UV light and exhibit a red luminescence corresponding to the electric dipole transition 5D0 → 7F2 at 615nm. The optimum doping in MY2−x Eu x (MoO4)4 (M=Ba, Sr, Ca) were investigated by the dependence of luminescence quantum efficiency (QE) on the Eu3+ concentrations. The absolute luminescence quantum efficiencies were measured for all the samples. The luminescence thermal satiability was checked by measuring the temperature-dependent luminescence intensities in temperature region of 10–450K. The results indicate that the three phosphors of BaYEu(MoO4)4, SrY0.6Eu1.4(MoO4)4 and CaEu2(MoO4)4 are the best choice for white-LEDs to be used for lighting. This was evaluated in details by taking into account of the properties such as the excitation spectra, the luminescence QEs, the red color coordinates, the luminescence quenching of Eu3+-doping concentrations and the thermal stability. [Copyright &y& Elsevier]

Abstract: The red-emitting phosphors Ca9Eu2W4O24 and Sr9Eu2W4O24 were synthesized by the solid-state reaction method. The crystal phases were characterized by X-ray powder diffraction. The photoluminescence excitation and emission spectra were investigated. The luminescence excitation and emission spectra confirm that the phosphors are efficiently excited by near UV light. The dependence of luminescence intensities on the heating temperatures was investigated. The Ca9Eu2W4O24 phosphor exhibits higher thermal stability than that of Sr9Eu2W4O24. The crystallographic sites for Eu3+ ions in Ca9Eu2W4O24 and Sr9Eu2W4O24 are investigated by the site-selective excitation spectra in the 5D0 → 7F0 wavelength region. It is identified that the Eu3+ ions occupy only M sites (statistically occupied by 0.5Eu and 0.5Ca) in Ca9Eu2W4O24 and, however, the Eu3+ ions can substitute both M sites (Eu3+ +Sr2+) and Sr2+ sites in Sr9Eu2W4O24. The luminescence spectra and the thermal stability are discussed on the basis of the crystal structure, Eu3+ site-distributions and the energy transfer. [Copyright &y& Elsevier]

Abstract: A series of red emitting phosphors Sr9Eu2W4−x Mo x O24 (x =0–4) have been synthesized by solid-state reactions and their crystal structures, photoluminescence properties were studied. The excitation and emission spectra of Sr9Eu2W4−x Mo x O24 phosphors can be modified by Mo6+ doping. As the molybdate content increased, the Eu3+ emission intensity of Sr9Eu2W4−x Mo x O24 (x =0–4) under 395nm excitation was found to increase and reached a maximum at x =2. The excitation spectra, the emission intensities and the chromaticity coordinates of Sr9Eu2W4−x Mo x O24 (x =2) were compared to those of the conventional red phosphor Y2O2S: Eu3+. The intense red-emission under near-UV excitation suggests that Sr9Eu2W4−x Mo x O24 (x =2) could be a potential candidate for white light generation by using near-UV LEDs. In this study, the effects of Mo6+ doping on the crystal structure and photoluminescence properties of Sr9Eu2W4−x Mo x O24 were discussed. [Copyright &y& Elsevier]

Abstract: Eu2+-activated Ba2CaMg2Si6O17 phosphors were synthesized by conventional solid-state reaction. The phase formation was confirmed by X-ray powder diffraction measurement. The photoluminescence excitation and emission spectra were investigated. The phosphor presents blue-emitting luminescence. The crystallographic sites of Eu2+ ions in Ba2CaMg2Si6O17 host were discussed on the base of luminescence properties and the crystal structure. The lightly Eu2+-doped sample shows one luminescence center for the Eu2+ ions on Ba2+ sites, while there are two luminescence centers for the Eu2+ ions on both the Ba and Ca sites in heavily Eu2+-doped sample. The dependence of luminescence intensity on temperatures and the activation energy (ΔE) for the thermal quenching were reported. The phosphor shows an excellent thermal stability on temperature quenching because of the special layered structure of Ba2+ ions in the interlayer between SiO4 layers. [Copyright &y& Elsevier]

A red-emitting phosphor, Eu3+-doped Ca9LiGd2/3(PO4)7, was synthesized by the conventional high-temperature solid-state reaction. X-ray powder diffraction (XRD) analyses confirmed the pure crystalline phase of Whitlockite-type structure. The excitation spectra of Eu3+doped Ca9LiGd2/3(PO4)7were measured in the VUV and UV region indicating an efficient energy transfer process from the host and Gd3+to Eu3+ions. Upon excitation with VUV and UV radiation, the phosphor showed strong red emission around 611 nm corresponding to the forced electric dipole 5D0→7F2transition of Eu3+ions. The VUV- and UV-excited luminescence spectra of Ca9LiGd2/3(PO4)7:Eu3+together with the dependence of the integrated emission intensities on the doping levels were investigated. The Eu3+ions were investigated by a tunable laser as an excitation source. The excitation spectra of 7F0→ 5D0transitions suggest that there are two families of inequivalent sites for Eu3+in this host. The concentration quenching and crystallographic site-occupancy of Eu3+ions in Ca9LiGd2/3(PO4)7host were discussed on the basis of the site selective excitation and emission spectra, the luminescence decay and its crystal structure. [ABSTRACT FROM AUTHOR]

The new red-emitting phosphors of Eu3+-doped borotungstate Gd4B2WO12 were prepared by the high-temperature solid-state reaction. The phosphors were characterized by X-ray powder diffraction technique. The photoluminescence excitation and emission spectra, the fluorescence decay curves and the dependence of luminescence intensity on temperature were investigated. The phosphor can be efficiently excited by near UV light to realize an intense red luminescence (618 nm) corresponding to the electric dipole transition 5D0→7F2 of Eu3+ ions. The crystallographic site-occupations of the Eu3+ ions in Eu4B2WO12 were investigated by the site-selective excitation and emission spectra, and the fluorescence decay curves in the 5D0→7F0 region using a pulsed, tunable, and narrowband dye laser. The concentration quenching of the red luminescence together with the thermal stability were discussed on the base of the Eu3+ site-distributions in Eu4B2WO12 host. [ABSTRACT FROM AUTHOR]

Abstract: Eu-based vanadate Ca9Eu(VO4)7 phosphor was synthesized by the solid state reaction method and was characterized by X-ray powder diffraction (XRD). The photoluminescence excitation and emission spectra, fluorescence decay curves and the dependence of luminescence intensity on temperature were investigated. The phosphor can be efficiently excited by near UV light to realize an intense red luminescence (614nm) corresponding to the electric dipole transition 5D0 → 7F2 of Eu3+ ions. The crystallographic site-occupations of the Eu3+ ions in Ca9Eu(VO4)7 were investigated by the site-selective excitation and emission spectra, and the fluorescence decay curves in the 5D0 → 7F0 region using a pulsed, tunable, narrowband dye laser. The red luminescence together with the thermal stability was discussed on the base of the Eu3+ site-distribution in Ca9Eu(VO4)7 host. [Copyright &y& Elsevier]

Abstract: Ce3+-doped Na2CaMg(PO4)2 was prepared by high temperature solid-state reaction. The phosphor was confirmed to be pure crystalline phase of Na2CaMg(PO4)2. The spectroscopic properties of the Ce3+ ions were investigated by vacuum ultraviolet spectroscopy. The energy transfer from the host to Ce3+ ions was demonstrated. The phosphor could be excited by VUV light and showed a broad purplish blue emission with the maximum wavelength at 385nm. The five 5d levels corresponding to the 4f1 →4f05d1 transition of Ce3+ ions were identified. The spectroscopic parameters, e.g., the barycenter, host absorption bands, crystal field splitting and stokes shift were discussed. [Copyright &y& Elsevier]

Abstract: A red-emitting phosphor of Eu3+-doped calcium–tellurium–zinc oxide, Ca3Te2(ZnO4)3, with a garnet-type structure was synthesized by high temperature solid-state reactions. This phosphor exhibited a strong red emission. The photoluminescence excitation spectrum showed that Ca3Te2(ZnO4)3:Eu3+ can be effectively excited by UV–visible light. The property of long-wavelength excitation for this material has a benefit as a red phosphor in application of white light-emitting diodes. The colour coordinates were calculated. The excitation and emission spectra and luminescence decay curves were obtained using a pulsed, tunable, narrowband dye laser. Crystallographic sites and charge compensation mechanism of Eu3+ ions were discussed. The emission line from Eu3+ in intrinsic crystallographic site in the lattice was located at 579.56nm. The emission line from Eu3+ in another disturbed site, which is created by the defects created by the charge-compensation, was located at 580.88nm. The disordered crystallographic sites of Eu3+ are benefit for their strong red luminescence corresponding to the 5D0→7F2 transition. [Copyright &y& Elsevier]

Abstract: Ce3+, Tb3+ and Ce3+ plus Tb3+ doped BaZn2(PO4)2 phosphors were prepared by a solid-state reaction under reductive atmosphere. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR) techniques confirmed the formation of BaZn2(PO4)2 crystal phase. BaZn2(PO4)2:Ce3+ showed the parity and spin allowed 5d–4f band emission of Ce3+ ions and BaZn2(PO4)2:Tb3+ phosphors exhibited the strong typical green emission of 5D4→7F5 at 543 nm. The presence of Ce3+ ions in BaZn2(PO4)2:Tb3+ phosphor resulted the enhancement of Tb3+ emission intensity. The Ce3+ and Tb3+ codoped BaZn2(PO4)2 phosphor showed the emission of Ce3+ ions and the characteristic emissions of Tb3+ transitions, namely, 5D3,4− 7FJ (, 5, 4, 3) are due to the efficient energy transfer from Ce3+ to Tb3+ in the host. [Copyright &y& Elsevier]

Abstract: BaBPO5:Sm3+ powder phosphor was prepared by solid-state reaction method and then irradiated with X-rays to investigate effects of radiation on electronic valence states of Sm ions. Reduction of Sm3+ to Sm2+ occurred by the X-ray irradiation on Sm3+:BaBPO5. As-prepared and X-ray-irradiated BaBPO5:Sm3+ show different excitation and emission spectra of Sm3+ and Sm2+ depending on exposure time of the X-ray irradiation. It was found that the reduction of Sm3+ after X-ray irradiation is very efficient and BaBPO5 is found to be a suitable host for Sm3+ →Sm2+ conversion. The thermal stability, the photo-bleaching and the thermo-luminescence (TL) of Sm2+ ions formed by X-ray irradiation were measured. The defect structures of Sm2+ ions in BaBPO5 have been discussed based on the experimental results. [Copyright &y& Elsevier]

Abstract: Sm3+ ions doped Olgite crystals (Ba,Sr)(Na,Sr)2Na[PO4]2 were prepared by high temperature solid-state reaction. Sm2+ ions were obtained by X-ray irradiation reduction. The samples were investigated by X-ray diffraction, SEM, photoluminescence and decay curves measurements. In (Ba,Sr)(Na,Sr)2Na[PO4]2, the influence of different mole ratios of Sr to Ba atoms on the crystal structure, reducing efficiencies of Sm3+ to Sm2+ and luminescence properties of Sm2+ ions were discussed. It is found that the conversion of Sm3+ →Sm2+ after X-ray irradiation is efficient in this phosphate. The emission of Sm2+ in this host after excitation into the 4f5 5d1 levels shows 5D0 → 7F J (J =0, 1, 2) emission together with a broad emission band. The characteristic of Sm2+ ions luminescence was discussed. [Copyright &y& Elsevier]

Abstract: The Eu3+ ions doped Ba3BP3O12 were prepared by high-temperature solid-state reaction method. The site-selective excitation and emission spectroscopy, and luminescence decay have been investigated in the 5D0 → 7F0 region under a pulsed, tunable, narrowband dye laser at RT and 10K. The emission only arises from the 5D0 level of Eu3+ ions. The study is focused on the distribution of Eu3+ sites which exhibit different spectroscopic features in Ba3BP3O12. Non-site-selective emission spectra under UV excitation were also performed. There exist two isolated Eu3+ crystallography sites in Ba3BP3O12, among which no energy transfers could be detected. The defect structures and charge compensation mechanism were discussed. [Copyright &y& Elsevier]

A self-activated yellow-emitting phosphor of nano-sized Cs 5 V 3 O 10 was synthesized by the Pechini method. The crystal phase and structure were investigated by X-ray diffraction (XRD) and structural refinement. The nanoparticles were characterized by scanning electron microscope (SEM) and X-ray photoelectron spectroscopic (XPS) measurements. Luminescence properties such as excitation and emission spectra as well as the absolute external quantum efficiency ( η ) are presented. Cs 5 V 3 O 10 is efficiently excited by UV light and X-ray and presents a bright yellow luminescence with the maximum η of 85.2%. It is suggested that Cs 5 V 3 O 10 is expected to be an efficient phosphor for lighting and display. [ABSTRACT FROM AUTHOR]

Abstract: A series of Eu2+-activated green-emitting phosphors, barium zinc silicate Ba2Zn3Si3O11:Eu2+, was first synthesized by chemical sol–gel method. The photoluminescence excitation and emission spectra, the concentration quenching of the phosphors, the luminescence color chromaticity and absolute quantum efficiency (QE), were measured. The results indicate that Ba2Zn3Si3O11:Eu2+ phosphors can be efficiently excited by not only UV- but also blue-LED chips to realize novel green-emitting luminescence corresponding to the electric-dipole allowed 4f–5d transition of the Eu2+ ions. Additionally, the luminescence was suggested to originate from two kinds of Eu2+ centers in terms of photoluminescence properties. The energy transfer between the Eu2+ centers was discussed by analyzing the photoluminescence spectra, concentration-dependent luminescence intensity and lifetimes. This is a potential candidate for the application to white LEDs because the tunable luminescence and small thermal quenching. [Copyright &y& Elsevier]

Abstract: Yb3+ stoichiometric ceramic sample Ca9Yb(VO4)7 was synthesized by the conventional high-temperature solid state reaction. The emission spectra and decay curves of both the near-infrared emission and the cooperative luminescence were measured. The sample presents the bright blue cooperative up-conversion luminescence centered at 480nm under the excitation of a 976nm laser diode (LD) at room temperature. The blue emission mechanism was discussed on the pump-power dependent emission intensity and the luminescence lifetimes. The up-conversion is assigned to cooperative de-excitation of Yb3+–Yb3+ pairs. [Copyright &y& Elsevier]

Abstract: Eu3+-doped borotungstate La1-x Eu x BWO6 (x=0.01–0.25) were synthesized by Pechini method. The red-emitting nano-phosphors were characterized by X-ray powder diffraction, scanning electron microscope and photoluminescence excitation and emission measurements. The optimal Eu3+ doping level of the phosphors was determined by the dependence of the red luminescence on the concentration. The abnormally high intensity of 5 D 0→7 F 4 transition from Eu3+ ions was observed in La1−x Eu x BWO6 (x=0.01–0.25). This nano-phosphor can be efficiently excited by near-ultraviolet and blue light to realize the far stronger red luminescence than the Y2O2S:Eu3+. [Copyright &y& Elsevier]

Abstract: The fully concentrated Eu3+-based molybdenum borate Eu2MoB2O9 was synthesized by the solid-state reaction method. The photoluminescence excitation and emission spectra, the temperature dependent luminescence intensities and the decay curve were investigated. Photoluminescence spectra show that the phosphor can be efficiently excited by near-UV light and exhibits an intense red luminescence corresponding to the electric dipole transition 5D0 → 7F2 at 615nm. The luminescence intensities and color purity were investigated by increasing the fired temperatures. The phosphor shows the stable luminescence and color purity at high temperature. [Copyright &y& Elsevier]

Abstract: A green-emitting phosphor of Eu2+-activated Sr5(PO4)2(SiO4) was synthesized by the conventional solid-state reaction. It was characterized by photoluminescence excitation and emission spectra, and lifetimes. In Sr5(PO4)2(SiO4):Eu2+, there are at least two distinguishable Eu2+ sites, which result in one broad emission situating at about 495nm and 560nm. The phosphor can be efficiently excited in the wavelength range of 250–440nm where the near UV (～395nm) Ga(In)N LED is well matched. The dependence of luminescence intensities on temperature was investigated. With the increasing of temperature, the luminescence of the phosphor shows good thermal stability and stable color chromaticity. The luminescence characteristics indicate that this phosphor has a potential application as a white light emitting diode phosphor. [Copyright &y& Elsevier]

Abstract: Eu2WO6 was synthesized by the conventional solid state reaction method. Crystal phase was characterized by the X-ray powder diffraction. The excitation and emission spectra indicate that this phosphor can be effectively excited by near UV (395 nm) and blue light (465 nm), and the emission spectra exhibit a satisfactory red performance at 611 nm, which is due to the characteristic 5D0−7F2 transitions of Eu3+ ions. The luminescence intensities and color purity were investigated by increasing the fired temperature. The phosphor shows stable luminescence and color purity at high temperature. [Copyright &y& Elsevier]

Abstract: Sm3+ ions doped NaSm0.01Ba0.78Sr0.21(PO4) was prepared by high-temperature solid-state reaction method. Sm2+ ions were obtained by X-ray irradiation reduction. The samples were investigated by X-ray diffraction, photoluminescence, and decay curves measurements. It is found that the conversion of Sm3+ →Sm2+ after X-ray irradiation is very efficient in this phosphate. NaSm0.01Ba0.78Sr0.21(PO4) is a suitable host for Sm3+ →Sm2+ conversion. The emission of Sm2+ in this host after excitation into the 4f55d1 levels shows 5D0 → 7FJ (J =0, 1, 2) emission together with the broad 5d→4f emission band at room temperature, while only the 5D0 → 7FJ (J =0, 1, 2) emission is observed at lower temperature. [Copyright &y& Elsevier]

[Display omitted] • Site-selective spectra have been measured on Eu3+-doped SrLa 2 Mg 2 W 2 O 12 and Sr 2 La 2 MgW 2 O 12. • Compared with Sr 2 La 2 MgW 2 O 12 :Eu3+, SrLa 2 Mg 2 W 2 O 12 :Eu3+ has more efficient luminescence and higher thermal stability. • Eu3+ only occupies La3+ in SrLa 2 Mg 2 W 2 O 12 , it replaces both Sr2+ and La3+ in Sr 2 La 2 MgW 2 O 12. Eu3+ is not only a major red-emitting activator, but also an excellent spectral probe ion. This work reports the Eu3+-sites and luminescence in the cation-deficient perovskite tungstates, A-site deficient SrLa 2 (Mg 2 W 2)O 12 [Sr 1/2 □ 1/2 La(MgW)O 6 ] and B-site deficient Sr 2 La 2 (MgW 2)O 12 [SrLa(Mg 1/2 □ 1/2 W)O 6 ]. The 7F 0 →5D 0 excitation spectra of Eu3+ activators in two lattices were measured via pulsed dye laser. In SrLa 2 (Mg 2 W 2)O 12 :Eu3+, there is only one 7F 0 →5D 0 transition, which could be related to the Eu3+ center on La3+ sites; while, two 7F 0 →5D 0 transitions in Sr 2 La 2 (MgW 2)O 12 indicate Eu3+ ions occupy Sr2+ in addition to La3+, resulting in the luminescent centers related to heterovalent substitution defects. The different Eu3+ sites make two phosphors exhibit different red luminescence properties. SrLa 2 (Mg 2 W 2)O 12 :Eu3+ shows higher luminescent efficiency and thermal quenching due to its regular distribution of the activators resulting in lower dispersion losses of the energy transfer. The experimental results show that rare earth ions occupy different crystallographic positions in A -site and B -site deficient perovskite oxides, and this microstructure can be important for the corresponding luminescent properties. [ABSTRACT FROM AUTHOR]

Abstract Gd 8 V 2 O 17 was prepared via the facile solid-state reaction. The optical absorption, temperature-dependent luminescence, and decay lifetimes were investigated. Gd 8 V 2 O 17 has a direct allowed electronic transition with band gap energy of 3.18 eV. Under the excitation of UV light, the phosphor shows the typical self-activated luminescence from the charge transfer (CT) transitions in VO 4 3− groups. The emission intensity has a nearly constant value from 10 to 150 K, while it increases above 150 K. And the emission has an abnormal blue-shift with the increase of temperature from 10 to 300 K, so the luminescence color varies from green to blue. Over the whole temperature ranges, the maximum emission wavelength showed a linear dependence on temperature; consequently, the temperature-dependent properties have a potential advantage in luminescence thermometry. The luminescence mechanism was discussed on the proposed two VO 4 emission centers and the energy transfer between them. Graphical abstract fx1 [ABSTRACT FROM AUTHOR]

Novel red-emitting Na 2 MgSiO 4 : Eu 3+ phosphors with different Eu 3+ contents were synthesized by sol-gel method. The crystal structure was confirmed by X-ray powder diffraction. The luminescence properties and decay curves were investigated. The optical Eu 3+ doping concentration of Na 2 MgSiO 4 : Eu 3+ is about 5 mol%. The excitation spectrum exhibits a broad band of 250–500 nm. The abnormal dominant emission peak of Na 2 MgSiO 4 : Eu 3+ phosphors excited effectively by 393.5 nm (near-UV) is located at 702 nm due to the 5 D 0 → 7 F 4 transition that caused by the highly polarizable chemical circumstance. The CIE chromaticity coordinate and the photoluminescence quantum yield of the Na 2 MgSiO 4 : 0.05Eu 3+ phosphor are (0.644, 0.355) and 65.81%, respectively. The mechanism of concentration quenching can be attributed to the dipole–dipole interaction between Eu 3+ ions and the thermal quenching might be ascribed to the competition between energy transfer and crossover process. [ABSTRACT FROM AUTHOR]

Polycrystalline phosphors YK 3 B 6 O 12 :RE 3+ (RE = Eu, Ce, Tb) were prepared by the solid-state synthesis. The single crystal-phases of the samples were confirmed by X-ray powder diffraction (XRD) measurements and the structural refinements. The field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), and electron dispersive X-ray (EDX) measurements were applied to analyze the morphologies of the phosphors. The photoluminescence excitation spectra (PLE) and emission (PL) spectra, decay curves and lifetimes were investigated. Under the near-UV light excitation, YK 3 B 6 O 12 :Eu 3+ , YK 3 B 6 O 12 :Ce 3+ , and YK 3 B 6 O 12 :Tb 3+ phosphors exhibit the characteristic emission transitions from Ce 3+ (5d→4f transitions in blue color), Eu 3+ ( 5 D 0 → 7 F 2 , red color), and Tb 3+ ( 5 D 4 → 7 F 5 , green color), respectively. The luminescence internal quantum efficiency (QE), the optimal doping level and the thermal stability with the activation energy (Δ E ) were measured. The result in this work could be useful for the further applications of this new host as a potential phosphor. [ABSTRACT FROM AUTHOR]

Eu 2+ -doped Mg 3 (BO 3 )F 3 phosphors were synthesized by solid-state reaction. The structural refinement, the luminescence and decay curves were investigated. The phosphor presents a broad emission band assigned to 4f 6 5d→4f 7 ( 8 S 7/2 ) transitions in blue range, which was overlapped with the peculiar 4f 7 ( 6 P 7/2 )→4f 7 ( 8 S 7/2 ) transitions even at room temperature. In addition, the 4f 7 ( 6 P 7/2 )→4f 7 ( 8 S 7/2 ) transition presents extremely strong intensity compared with the peculiar 4f 7 ( 6 P 7/2 )→4f 7 ( 8 S 7/2 ) transitions. The decay properties and the thermal activation energy (Δ E ) were reported. It shows high activation energy of 0.71 eV on temperature quenching. The maximum absolute quantum efficiency (QE) was measured to be 83% under UV light. The phosphor could deserve further investigations because of its peculiar spectral characteristics for basic studies and excellent application performances. [ABSTRACT FROM AUTHOR]

Highlights: [•] Na5YZrSi6O18 was firstly developed to be a new bluish green-emitting silicate. [•] Na5YZrSi6O18 presents unusual properties: efficient excitation and longer emission wavelength. [•] Na5YZrSi6O18 shows long-lasting phosphorescence with duration time above 3h. [Copyright &y& Elsevier]

Abstract: A new blue-emitting nanophosphor of Eu2+-activated BaCa2Al8O15 was synthesized by the Pechini method. The phosphors were investigated by X-ray powder diffraction (XRD) measurement and confirmed to be a pure crystalline phase of BaCa2Al8O15. The photoluminescence excitation and emission spectra, the luminescence decay and the color coordinates were taken to investigate the luminescence characteristics. The dependence of luminescence intensities BaCa2Al8O15:Eu2+ on the doping concentrations was investigated. This nanophosphor can be efficiently excited by UV light and presents bright blue luminescence. Under the same conditions, the light yield of BaCa2Al8O15:Eu2+ is about 1.2 times higher than that of blue-emitting phosphor BaMgAl10O17:Eu2+. Eu2+-activated BaCa2Al8O15 nanophosphor exhibits the long-lasting phosphorescence, which was analyzed by measuring the afterglow decay curves. The co-doped Eu3+ ions and some defects were suggested to be the possible trap-centers. [Copyright &y& Elsevier]

Abstract: A series of Ba2Mg1−x Mn x P4O13 (x =0–1.0) and Ba1.94Eu0.06Mg1−x Mn x P4O13 (x =0–0.15) phosphors were prepared by conventional solid-state reaction. X-ray powder diffraction (XRD), the photoluminescence spectra, and the decay curves are investigated. XRD analysis shows that the maximum tolerable substitution of Mn2+ for Mg is about 50mol% in Ba2MgP4O13. Mn2+-singly doped Ba2MgP4O13 shows weak red-luminescence peaked at about 615nm. The Eu2+/Mn2+ co-doped phosphor emits two distinctive luminescence bands: a blue one centered at 430nm originating from Eu2+ and a broad red-emitting one peaked at 615nm from Mn2+ ions. The luminescence of Mn2+ ions can be greatly enhanced with the co-doping of Eu2+ in Ba2MgP4O13. The efficient energy transfer from Eu2+ to Mn2+ is verified by the excitation and emission spectra together with the luminescence decay curves. The emission colors could be tuned from the blue to the red-purple and eventually to the deep red. The resonance-type energy transfer via a dipole–quadrupole interaction mechanism is supported by the decay lifetime data. The energy transfer efficiency and the critical distance are calculated and discussed. The temperature dependent luminescence spectra of the Eu2+/Mn2+ co-doped phosphor show a good thermal stability on quenching effect. [Copyright &y& Elsevier]

Abstract: A new phosphor of Eu2+-doped Cs2MgSi5O12 was synthesized by conventional solid-state reaction. The phase formation was confirmed by X-ray powder diffraction measurements. The photoluminescence excitation and emission spectra were measured. The phosphor presents bright yellowish-green-emitting luminescence. The site-occupancy of Eu2+ ions doped in Cs2MgSi5O12 was discussed according to the crystal structure and the luminescence characteristics of Eu2+ ions. Two different Eu2+ centers were assigned in Cs2MgSi5O12 lattices. The dependence of luminescence intensity on the heating temperatures was measured and discussed. The chromaticity coordinates and activation energy (ΔE) for the thermal quenching of Cs2MgSi5O12:Eu2+ were reported. [Copyright &y& Elsevier]

• Te 3 Nb 2 O 11 is a narrow band semiconductor with heavy dispersion between Nb-3d and Te-5s CB. • Intrinsic luminescence and decay time of Te 3 Nb 2 O 11 were reported. • Surface oxygen vacancies can be induced on Te 3 Nb 2 O 11 :Eu3+ on via low-temperature annealing. • Both luminescence and photocatalysis were all enhanced by the surface defects. • Active paths of light-created charges were demonstrated. Luminescence and photocatalysis are two important properties of optical materials for photoenergy conversion. In this work, pure- (TNO) and Eu3+-doped-Te 3 Nb 2 O 11 (TNO:Eu) were prepared by sol–gel method combined with solid-state reaction routine. Te 3 Nb 2 O 11 shows an intrinsic luminescence band peaked at 485 nm, which was quenched after Eu3+ doping. TNO:Eu presents red-emitting color from radiative transitions 5D 0 → 7F J (J = 0–4) of Eu3+ ions. Surface oxygen vacancies could be successfully induced on Eu3+-doped-Te 3 Nb 2 O 11 nanoparticles via low-temperature annealing in the CO atmosphere. The annealed TNO:Eu sample with surface oxygen vacancies can narrow the bandgap via broadening the valence band. Both red-luminescence and photocatalysis were greatly enhanced after the annealing treatments. The surface oxygen vacancies were verified by the measurements such as X-ray photoelectron spectroscopy (XPS), Raman spectra, induced optical absorption, and electron paramagnetic resonance (EPR), etc. It could be suggested that fast decay time (6.14 μs) of Te 3 Nb 2 O 11 causes an efficient recombination of the light-induced charges. The introduction of different Eu3+ midgap states in TNO:Eu provides longer decay time (1.25 ms) for the excited states improving charge-separation upon photo-excitation during photocatalysis. [ABSTRACT FROM AUTHOR]

A series of novel red-emitting phosphor of Li 5 La 3–3x Eu 3x Ti 2 O 12 (x = 0.01–0.25) were synthesized via the facile solid-state reaction method. The Rietveld refinements verified that all the samples crystallized in a garnet-like cubic structure. The band gap energy of Li 5 La 3 Ta 2 O 12 is 3.87 eV, which can be greatly narrowed by Eu 3+ -doping. This benefits the red-shift of optical absorption from UV- to near-UV light region. Importantly, the sample presents dominant absorption in near-UV (390–395 nm) and blue-light (460–465 nm) region. Li 5 La 3–3x Eu 3x Ta 2 O 12 (x = 0.01–0.15) has a bright red-luminescence with the strongest 5 D 0 → 7 F 2 transition at 613 nm. The energy transfer was discussed on the Eu 3+ -doping concentration. The experimental red-emitting lamps were fabricated using a 395 and a 460 nm LED-chips, respectively, in combination with the single phosphor of Li 5 La 3–3x Eu 3x Ta 2 O 12 (x = 0.2) driven by 2 mA current. The results indicate that the phosphor could be a promising candidate used in solid-state lightings and displays. [ABSTRACT FROM AUTHOR]

Series of Mn 4+ -activated LiLa 2 NbO 6 red emitting phosphors were prepared by the solid state method. The structural and luminescence properties are investigated on the basis of X-ray diffraction (XRD), emission and excitation spectra, and luminescence decay curves. The LiLa 2 NbO 6 :Mn 4+ phosphors can be efficiently excited by near-UV to blue light and exhibit bright red emission at around 712 nm, which can be assigned to the 2 E g → 4 A 2g transition of the 3 d 3 electrons in [MnO 6 ] octahedra. Temperature dependent emission spectra and decay curves from 10 to 480 K are analyzed to understand the luminescence mechanism of Mn 4+ in LiLa 2 NbO 6 lattice. Notably, such a novel red emitting phosphor shows special anti-thermal quenching behavior. [ABSTRACT FROM AUTHOR]

Ba 5 Al 3 F 19 :Eu 2+ blue-emitting phosphors were synthesized by the solid state reaction in a reductive atmosphere. The crystal structure of Ba 5 Al 3 F 19 :Eu 2+ phosphors were characterized by using the X-ray powder diffraction (XRD) measurement. The luminescence properties are investigated systematically based on the crystal structure. Emission and excitation spectra of the Ba 5 Al 3 F 19 :Eu 2+ phosphor along with the decay curves were characterized. Under the excitation of UV light, the phosphor exhibits a broad band emission around 410 nm ascribed to the allowed 4 f 6 5 d →4 f 7 ( 8 S 7/2 ) transition, together with a sharp line at 360 nm corresponding to the forbidden 4 f 7 ( 6 P 7/2 )→4 f 7 ( 8 S 7/2 ) transition of the Eu 2+ ions. The temperature dependent emission spectra and decay curves were measured to investigate the origins of the emission and the thermal stabilities of the as-prepared phosphors. The as-prepared Ba 5 Al 3 F 19 :Eu 2+ phosphors display interesting and stable luminescence properties, which can act as promising blue-emitting phosphor candidates. [ABSTRACT FROM AUTHOR]

Eu 3+ -doped perovskite-related tungstate Ba 4 Na 2 W 2 O 11 was synthesized by high-temperature solid state reaction. The red-emitting phosphor was characterized by X-ray powder diffraction, structural refinement, and scanning electron microscope and photoluminescence excitation and emission measurements. The optimal doping concentration of Ba 4 Na 2 W 2 O 11 :Eu 3+ is about 7 mol%. This phosphor can be efficiently excited by near-ultraviolet and blue light to realize the stronger red luminescence than the Y 2 O 2 S:Eu 3+ phosphor. The phosphor presents the dominated 5 D 0 → 7 F 1 transition at a low doping level, and the 5 D 0 → 7 F 2 transition becomes the strongest one in the Eu 3+ -heavily doped samples. The doping induces the luminescence color changing from reddish-orange to pure red. The photoluminescence properties of the phosphor are discussed on the base of the crystal structure. [ABSTRACT FROM AUTHOR]

Abstract: A yellow-emitting nanophosphor of Ce3+-activated Sr3LuAl2O7.5 was prepared by chemical sol–gel method. The X-ray powder diffraction and scanning electron microscopy were applied to characterize the phosphors. The luminescence properties such as the photoluminescence (PL) excitation and emission spectra, the internal quantum efficiency (QE) and the luminescence decay curve (lifetime) were investigated. The Ce3+-activator concentration has an influence on the luminescence properties. Ce3+-activated Sr3LuAl2O7.5 exhibits brightest yellow emission with the internal quantum efficiency of 57%. The thermal stability of the yellow-emitting phosphor was evaluated by the temperature-dependent luminescence and the activation energy for thermal quenching. The luminescence properties of Ce3+-activated Sr3LuAl2O7.5 was discussed in comparisons with famous yellow-emitting YAG:Ce3+. This new nanophosphor could be a potential yellow-emitting phosphor for an application in lighting and display. [Copyright &y& Elsevier]

The title compounds are synthesized by solid state reactions of stoichiometric mixtures of CaCO3, Nb2O5, and Ln2O3 (Ln: La, Sm, Eu, Gd, Dy, Er, Yb, Y) at 1300-1350 °C for 20-48 h twice. [ABSTRACT FROM AUTHOR]

Abstract: Zr4+- and Eu3+-codoped SrMg2(PO4)2 phosphors were prepared by conventional solid-state reaction. Under the excitation of ultraviolet light, the emission spectra of Sr0.95Eu0.05Mg2−2x Zr2x P2O8 (x =0.0005–0.07) are composed of a broad emission band peaking at 500nm from Zr4+-emission and the characteristic emission lines from the 5D0 → 7F J (J =0, 1, 2, 3 and 4) transitions of Eu3+ ions. These phosphors show the long-lasting phosphorescence. The emission color varies from red to white with increasing Zr4+-content. The white-light emission is realized in single-phase phosphor of Sr0.95Eu0.05Mg2−2x Zr2x P2O8 (x =0.07) by combining the Zr4+- and Eu3+-emission. The duration of the persistent luminescence of Sr0.95Eu0.05Mg2−2x Zr2x P2O8 (x =0.07) reaches nearly 1.5h. The time at which the long-lasting phosphorescence intensity is 50% of its original value (T 0.5) is 410s. The afterglow decay curves and the thermoluminescence spectra were measured to discuss this long-lasting phosphorescence phenomenon. The co-doped Zr4+ ions act as both the luminescence centers and trap-creating ions. [Copyright &y& Elsevier]

• A new kind of rare-earth-free phosphor of Na 2 Mg 5 Si 12 O 30 :Mn2+ was developed. • Bright red emission was realized in Mn2+ 7.0 mol% doped Na 2 Mg 5 Si 12 O 30. • new emission appear at higher Mn2+ due to the formation of new Mn2+ centers. • The red phosphor shows high thermal stability compared with other reported ones. Na 2 Mg 5(1-x) Si 12 O 30 :5xMn2+(x = 0.005, 0.01, 0.03,0.05,0.07 and 0.09) red phosphors were synthesized by solid state reactions. The formation of a single phase compound is verified through the X-ray diffraction (XRD) studies. The excitation and emission spectra, and decay curves of Na 2 Mg 5 Si 12 O 30 :Mn2+ are investigated by optical and laser excitation spectroscopy in the temperature range 7–520 K. The strong red emission peaking at 600 nm is observed due to the spin forbidden transition 4T 1 → 6A 1 of Mn2+ ions. At high Mn2+ concentration, new side bands appear at lower energy side at around 670 nm which can be ascribed to the appearance of the formation of new Mn2+ centers. In addition, the thermal quenching behavior is investigated to evaluate the commercial value of Na 2 Mg 5 Si 12 O 30 :Mn2+ as red-emitting materials. [ABSTRACT FROM AUTHOR]