Emission Phosphor Research Articles

Spectral change and far-red emission of Mn2+ ions co-doped NaSrB5O9:Dy3+ luminescence material for plant growth LEDs

Due to the characteristic emission of phosphors, phosphor-converted LEDs have been employed to provide the requisite light sources for indoor plant growth in the optical agricultural industry. Herein, we prepared a series of Mn2+ co-doped NaSrB5O9:Dy3+ phosphors via a solid-state reaction method. These phosphors have significant three-band emissions at 467 nm (blue region), 606 nm (orange region), and 765 nm (far-red region), ascribed to the 4F9/2-6H15/2 and 4F9/2-6H13/2 transitions of the Dy3+ ions and the 4T1g(G)-6A1g(S) spin-forbidden transition of the Mn2+ ions, respectively, when excited by light of 376 nm (near-UV region). The co-dopant in the host material facilitates tunable photoluminescence (PL) due to energy transfer from the Dy3+ ions to the Mn2+ ions. The three emission peaks from the prepared phosphors well match with the absorption spectra of the photosynthesis pigments of plants, chlorophyll and phytochrome, which can absorb blue (400–500 nm), orange-red (550–700 nm), and infrared (IR) radiation, indicating that these phosphors have potential applications in the fabrication of plant-growth LEDs. Prior to the PL studies, the structure of the phosphors was determined by X-ray diffraction, refined by Rietveld method and chemically quantified by X-ray photoelectron spectroscopy.

The structure and photoluminescence properties of a novel yellow-green emission phosphor Ba3Sc2B4O12: Ce3+ excited by NUV light

A kind of borate mineral (Ba3Sc2B4O12) based Ce3+ doped phosphor is prepared by high thermal solid state reaction successfully. Its crystal and energy band is studied in detail by TEM, XRD and First Principle calculation. Ba3Sc2B4O12 crystallizes by trigonal system and P-3m1(164) space group. Series of Ce3+ doped Ba3Sc2B4O12 phosphors are researched. The energy band, electron cloud density and luminescent properties of Ba3Sc2B4O12: Ce3+ are investigated in great detail by density functional theory calculations, emission-excitation spectra, decay times and thermal dependent spectra. Ba3Sc2B4O12: Ce3+ can yield blue-green-yellow broad light at ~539 nm with FWHM 190 nm upon 370 nm light stimulation and the quantum efficiency is 22.7%. According to electron cloud density and photoluminescence (PL) property analysis, Ce3+ can occupy two kinds luminescent centers. White-LED is also fabricated combining with NUV chip covered by this phosphor and (Ca, Sr)AlSiN3: Eu2+ mixture driven by 3 V and 25 mA. It can generate warm-white light with 4180 K correlated color temperature. It demonstrates that Ba3Sc2B4O12: Ce3+ is a kind of RGB phosphor to get warm white light combining with NUV LED chip.

Color tuning of the Ba1.96Mg(PO4)2:0.04Eu2+ phosphor induced by the chemical unit co-substitution of the (BO3)3− anion group

Replacing the tricolor blend of phosphors by a single-phase white-emitting phosphor has emerged as a new technology for devising white-light-emitting diodes (WLEDs). Modification of the local structure in the crystal plays the key role in obtaining a single-phased, high CRI white-emitting phosphor. This process can also be employed to tune the color emission of the phosphor, especially those doped with Eu2+ ions. In this context, the selection of an appropriate host and the substituting chemical unit plays a vital role, as the crystal environment of the host greatly influences the photoluminescence (PL) emission of the Eu2+ ions. Herein, the color tuning of a new single-phase solid-solution Ba1.96Mg(PO4)2−x(BO3)x:0.04Eu2+ (x = 0.2, 0.5, 0.7, 1, 1.2 and 1.5) phosphor synthesized by the sol-gel/Pechini method is demonstrated. The structural variation induced by the varying composition of the borate (BO3)3− unit was analyzed by X-ray diffraction and Rietveld refinement studies. Fourier transform infrared spectroscopy revealed the presence of the vibrations corresponding to both the BO3 and PO4 chemical groups in the Ba1.96Mg(PO4)2−x(BO3)x:0.04Eu2+ phosphor. Morphological variations were also observed with the chemical co-unit substitution, which was analyzed with Scanning Electron Microscopy (SEM). PL studies indicated that the color tuning from blue-white-orange light, under near UV excitation, was achieved by varying the composition of the (BO3)3− group. The co-existence of the PO4 and BO3 groups gave rise to a higher-energy emission (420 nm) and a lower-energy emission (585 nm), respectively. The PL decay curves were analyzed to estimate the energy transfer efficiency between the higher-energy and lower-energy emission sites of the phosphor. This work presents a new strategy to tune the color emission of a singly-doped phosphor by modifying the structure of the host lattice.

Non-point source pollution in response to rural transformation development: A comprehensive analysis of China's traditional farming area

Controlling non-point source pollution (NPSP) has been viewed as a priority for realizing rural sustainability. Substantial literature has examined the effects of economic growth or urbanization on NPSP, while little work has been undertaken to investigate how rural transformation development (RTD) influence NPSP, and how differences in the process itself affect the impact that RTD has on such emissions. To fill these gaps, this paper empirically and comprehensively investigates the multiple effects of RTD on NPSP, by addressing three different dimensions of the RTD process-namely, regional urbanization, agricultural modernization, and land use transition. Longitudinal trends analysis of NPSP loads over the long-term (1990–2017) using the approach of inventory analysis was conducted to overcome the difficulty in gathering pollution monitoring data. Our results suggest that RTD generally presents an inverted “U” shaped relationship with NPSP, and differentiated evolution trajectories exist between different dimensions of RTD and different components and sources of NPSP. The turning points of total phosphor (TP) and planting industry-induced NPSP emission appear later than others. Land use transition and agricultural modernization process have significantly positive relations with the emissions from the planting industry. Furthermore, the evolution of NPSP is highly coupled with the shifts in national strategies, agricultural policies, and environmental regulations. These findings provide insights into the human-environment relation, suggesting that reasonable countermeasures should be formulated corresponding to the development stage of RTD.

On the Crystal Structure and Temperature Dependent Spectroscopy of the UV-C Emitting Phosphor Sr3(BO3)2:Pr3+,Na+

This work relates to the synthesis, structural, and spectroscopic characterization of praseodymium and sodium co-doped Sr3(BO3)2. This material was evaluated concerning its suitability as a photo- or radioluminescent UV-C emitting compound. Beyond recording the photoluminescence and radioluminescence, diffuse reflectance and temperature dependent spectra were recorded. Furthermore, the structure refinement based on single crystal X-ray diffraction data as well as morphologic studies by using scanning electron microscopy and dynamic light scattering methods were performed.

Controllable luminescence and efficient energy transfer investigation of a novel white light emission phosphor Ca19Na2Mg(PO4)14: Dy3+, Tm3+ with high thermal stability

White light emission phosphors are widely researched for application in lighting and display fields. However, the poor thermal stability is a real problem for the known single-phased white phosphors, which limits their further application. In this paper, Ca19Na2Mg(PO4)14: xDy3+, yTm3+ (CNMP, 0 ≤ x ≤ 0.06, y = 0, 0.01) phosphors with adjustable emission and good thermal stability are synthesized. The X-ray diffraction and X-ray energy dispersive spectrometer measurement distinctly confirm the successful synthesis of CNMP: xDy3+, yTm3+ (CNMP, 0 ≤ x ≤ 0.06, y = 0, 0.01). The photoluminescence results reveal that CNMP: Dy3+ shows characteristic excitation peaks in the range of 350–450 nm, and mainly exhibits strong yellow emission around 575 nm ascribed to the 4F9/2-6H13/2 transitions of Dy3+. To compensate the deficiency of blue light emission of CNMP: Dy3+, the trivalent Tm3+ ion is co-doped owing to its characteristic blue emission at 450 nm due to its 1D2-3F4 transitions. Therefore, the emission of CNMP: Dy3+, Tm3+ can be tuned from blue light region with CIE coordinates of (0.1649, 0.0387) to white light region with CIE coordinates of (0.3001, 0.3003) and finally move to yellow light region with CIE coordinates of (0.3732, 0.4493) through adjusting the doping ratio of Dy3+/Tm3+. The energy transfer efficiency and the energy transfer mechanism from Tm3+ to Dy3+ are further investigated. Moreover, CNMP: Dy3+, Tm3+ exhibites a high thermal stability and the emission intensity still keeps 84% of the initial intensity of Dy3+ at 230 °C. These outstanding properties show that Ca19Na2Mg(PO4)14: Dy3+, Tm3+ have great advantages and potentiality for applying in solid state lighting.

Novel thermally robust warm white light emitting phosphor Ca18Li3Y(PO4)14:Dy3+: Synthesis, crystal structure and luminescence property investigation

To explore novel single phase warm white light emitting phosphor, a series of phosphate phosphors Ca18Li3Y(PO4)14:Dy3+ were prepared. The phase purity, crystal structure, morphology and element component were confirmed by XRD Rietveld structure refinement, SEM and EDS analysis. The luminescence process of Ca18Li3Y(PO4)14:Dy3+ were systematically studied by photoluminescence spectroscopy and decay curves. The results indicated Ca18Li3Y(PO4)14:Dy3+ phosphors had strong excitation from 300 nm to 420 nm. Under the excitation of 350 nm, warm white light emission was achieved with the CIE color coordinates of (0.399, 0.448) and low CCT of ~ 3992 K. The concentration quenching mechanism and quantum efficiency of Dy3+ in Ca18Li3Y(PO4)14:Dy3+ were calculated and discussed in detail. The thermal quenching behavior revealed that Ca18Li3Y(PO4)14:Dy3+ had excellent thermal stability with stable color rendition. The thermal activation energy was finally calculated. All the results indicated the potential application of Ca18Li3Y(PO4)14:Dy3+ white light emission phosphor to be used in solid state lighting.

Absolute environmental sustainability assessment of a Danish utility company relative to the Planetary Boundaries

AbstractIncreasing environmental pressure from production and consumption of products and services is starting to affect Earth System stability. Thus, the Planetary Boundaries framework introduced a set of absolute boundaries for keeping the Earth System stable and delimiting a safe operating space for humanity. The sum of environmental pressures associated with human activities should not exceed the safe operating space. This includes utility companies whose activities relate to supply of water and treatment of waste‐ and stormwater. This study conducted an absolute environmental sustainability assessment (AESA) of a Danish utility company to evaluate if it could be considered absolutely sustainable relative to an assigned share of the safe operating space (SoSOS). The AESA evaluated the company's impacts relative to an assigned share of the Planetary Boundaries and relative to specific local boundaries for nitrogen and phosphorous emissions. Results showed that the assigned SoSOS was exceeded for 10 of 18 impact categories, for example, climate related boundaries were exceeded by up to a factor 7.8 while local nitrogen and phosphorus boundaries were exceeded by ca. a factor 16. The AESA can indicate to which degree the company exceeds its assigned SoSOS for certain impact categories and the processes and life‐cycle stages to focus on to become absolutely sustainable. This information is crucial for deriving specific impact reduction targets as part of environmental strategies for companies to become sustainable in an absolute sense.

Luminescence improvement of Sm3+ doped fluoro-phosphate glass by silver species

Sodium fluoro-phosphate glasses co-activated with Sm3+ ions and silver nanoparticles (NPs) were prepared. X-ray diffraction pattern shows the formation of crystalline silver phases embedded in the glassy host. The Raman spectroscopy, TEM measurements, optical absorption, and photoluminescence (PL) results indicated that the evolution of Ag species (including Ag+, molecular-like Ag clusters, and Ag nanoparticles) is very sensitive to the amount of silver introduced in the host matrix. The absorption spectra show the apparition of a new visible absorption band assigned to the surface Plasmon resonance (SPR) of silver nanoparticles (Ag NPs), for high Ag doping levels. Based on absorption and PL spectra, the Judd-Ofelt parameters and radiative properties of Sm3+ ions were evaluated. A significant improvement of both PL intensity and PL lifetime is noted. All the obtained results are encouraging for possible application of Sm3+ doped fluoro-phosphate glasses sensitized from Ag species in laser emission and LEDs phosphors.

The influence of the complexing agent on the luminescence of multicolor-emitting Y2O3:Eu3+,Er3+,Yb3+ phosphors obtained by the Pechini's method

In this study, it is reported the enhancement of the downshifting and the upconversion emission of Y2O3:Eu3+,Er3+,Yb3+ phosphor drove by sorbitol instead of the classic ethylene glycol used as polymerizing agent in the Pechini's synthesis. The RE3+ doping concentration was also varied to optimize the red or the green Er3+ emission or the Eu3+ red emission. Phosphors were obtained as high-crystalline and micro-sized particles, yet the doping concentration and the polymerizing agent influence the crystallite size and the lattice strain of the Y2O3 matrix that features optical band gap near to 5.6 eV. Under excitation at 378 nm, the downshifting emissions of Eu3+ and Er3+ are noticed, but under excitation at 463 nm, only the typical Eu3+ emission in the red spectral region is viewed. Contrarily, by exciting the phosphors at 980 nm within the IV spectral region, both green and red emissions of Er3+ plus the red emission of Eu3+ are seen through upconversion emission, and in this case, the pair Er3+/Yb3+ acts as sensitizers to the Eu3+ luminescence. Moreover, the use of sorbitol instead of ethylene glycol in the Pechini's synthesis enhances both downshifting and upconversion luminescence of phosphors due to a lowering of the Eu3+ local microssymmetry played by sorbitol, accordingly to the analyses of Judd-Ofelt intensity parameters of the phosphors. Finally, by varying the doping concentration, the polymerizing agent, and the excitation wavelength, the phosphor emission color may be tuned from the green towards the red spectral region.

Highly efficient yellow‐orange emission and superior thermal stability of Ba2YAl3Si2O12:Ce3+ for high‐power solid lighting

AbstractWith great economic benefits, white LEDs (w‐LEDs) have aroused worldwide attention. For phosphor‐converted w‐LED, highly efficient emission and good thermal stability of phosphor are significant parameters in practical application. Here, a yellow‐orange garnet‐structural phosphor, Ba2YAl3Si2O12:xCe3+ (x = 0‐0.1) (BYAS:xCe3+) was developed by solid solution design. The broad emission spectrum of the as‐synthesized phosphor could guarantee the effective increase of the color rendering index when it is combined with the InGaN blue chip. Benefiting from the garnet‐type highly rigid framework, BYAS:xCe3+ exhibits an excellent thermal stability (50%@673K of the initial integrated intensity at 280 K) as well as high absolute quantum efficiency (80.4%@460 nm excitation light). Utilizing the approach of “phosphor‐in‐glass” (PiG), a high‐power warm w‐LED is achieved based on a blue LED plus PiG and the illuminance of this w‐LED device can be as high as 4227 lx.

A blue and Red Bicolor Emission Phosphor Excited by a Single n-UV and Its Self-reduction of Eu3+ → Eu2+ in Na2Al2B2O7

It has great significance to find a path on generating multicolor with one n-UV chip coated with single phosphor. Herein, Eu doped Na2Al2B2O7 (NAB) phosphor is synthesized by solid state reaction in air atmosphere. Both 4f65d1 → 4f7 transitions of Eu2+ (445 nm) and f–f transitions as 5D0 → 7FJ (J = 0, 1, and 2) of Eu3+ (570–650 nm) have been observed. When increasing Eu doping concentration, both the luminescence intensity and lifetime of Eu3+ are increased and no obvious concentration quenching is observed, while the emission strength of Eu2+ does not change monotonically but with two remarkable peak values. The optimum doping concentration of Eu is 16%. Furthermore, Eu3+ is determined to be from Eu(BO3) matrix itself, and Eu2+ testified by ESR and XPS is created by self-reduction of Eu3+ to Eu2+ in NAB due to charge compensation. When x ≥ 0.16, the Eu3+ ion would rather bond with BO3 triangles in Eu(BO3) than stay as Eu2+ in AlO4 tetrahedral in NAB. Furthermore, the as prepared sample shows an excellent thermal stability and the PL quantum efficiencies of NAB: 0.16Eu sample excited by 341 nm and 393 nm are 11.99% and 9.39%, respectively. Additionally, the calculated CIE chromaticity coordinates signify that a couple of colors can be generated by adjusting the excitation wavelength owing to the strength changes between blue and red emissions. Therefore, this novel bicolor phosphor can serve as a potential candidate for w-LEDs applications.

Enhancing luminescent down-shifting of Eu-doped phosphors by incorporating plasmonic silver nanoparticles for silicon solar cells

This study experimentally demonstrated enhanced fluorescence emissions from luminescent down-shifting (LDS) Eu-doped phosphors under the effects of localized surface plasmon resonance (LPSR) from silver nanoparticles (Ag NPs). The plasmonic effects of the Ag NPs was examined in terms of plasmon-enhanced Raman scattering and plasmonic absorption. The fluorescence emission of the Eu-doped phosphors was examined in terms of photoluminescence (PL). Overlap between the plasmonic absorption band of Ag NPs and the PL emission band of Eu-doped phosphors increased fluorescence emissions by enhancing excitation. This study also developed an optical process model describing LSPR (Ag NPs), LDS (Eu-doped phosphors), and plasmon-enhanced fluorescence (PEF; Eu-doped phosphors with Ag NPs) on silicon solar cells. PEF was experimentally confirmed in terms of PL, external quantum efficiency (EQE), and photovoltaic current–voltage measurements. Compared to the cell with only an anti-reflection layer of SiO2/SOG, the inclusion of Ag NPs with the Eu-doped phosphors enhanced the PL emission intensity by 1.1243 times at a wavelength of 514 nm and also improved the EQE response by 8.3% (from 57.28% to 62.05%) and conversion efficiency by 7.1% (from 12.04% to 12.89%).

Enhancement of luminescence properties of SrTiO3:Sm3+ nanophosphor by charge compensator Li+ ion

Abstract In the current article, strontium titanate (ST) phosphor material doped with 1–9 mol% samarium ion (Sm3+) is prepared by facile solution combustion route. Characterizations for the prepared sample was carried out via powder X-ray diffraction, scanning and transmission electron microscopy, ultraviolet visible and Fourier transform infrared spectroscopy. Photoluminescence (PL) emission and excitation spectra were studied to examine the luminescence property of ST: Sm3+ nanophosphor. The ST: Sm3+ phosphor emission spectra were credited to the intra 4f orbital transition from the 4G5/2 level to the 6HJ (J = 5/2, 7/2, and 9/2). The presence of co-doped Li+ ion nanophospor increases the emission intensity of orange-red emission to multiple times. The improvement in the intensity of emission is attributed to the neighborhood symmetry around the Sm3+ and expansion in the crystallattice. The mechanism of PL enhancement in ST: Sm3+ nanophosphor with Li+ ion co-doping is discussed in detail. The optimized concentration of Sm3+ ions chromaticity coordinates were determined to be x = 0.59, y = 0.4. This favors in warm orange-red light emissive display applications.

Photoluminescence investigation in tungstate based materials

Tungstate based phosphor materials are very much promising because of their emerging application in various fields including optoelectronic devices, display devices, sensors, anti-counterfeiting, bioimaging, etc. In the present work, Er3+: MgWO4 phosphors have been synthesized via conventional solid state reaction method. The phase formation of the phosphors is confirmed by X-ray diffraction analysis. The vibrational modes and phonon frequency of the prepared phosphors have been investigated by FTIR analysis. Upon 980 nm diode laser excitation, the Er3+: MgWO4 phosphors exhibit several upconversion (UC) emission bands peaking at ∼489 nm, ∼523 nm, ∼545 nm, ∼655 nm and ∼800 nm. The pump power dependent UC emission study of the Er3+: MgWO4 phosphors has been carried out. The responsible mechanisms for the UC emission in the present phosphors have been explained by schematic energy level diagram. The reason behind the concentration quenching phenomenon has been discussed. The CIE chromaticity coordinates of the present phosphors have been calculated using GoCIE software. Thus, the synthesized phosphors can be suitably applicable in NIR to visible upconverter, temperature sensing, security ink and solid state lighting purposes.

Implementing Defects for Ratiometric Luminescence Thermometry.

In luminescence thermometry enabling temperature reading at a distance, an important challenge is to propose new solutions that open measuring and material possibilities. Responding to these needs, in the nanocrystalline phosphors of yttrium oxide Y2O3 and lutetium oxide Lu2O3, temperature-dependent emission of trivalent terbium Tb3+ dopant ions was recorded at the excitation wavelength 266 nm. The signal of intensity decreasing with temperature was monitored in the range corresponding to the 5D4 → 7F6 emission band. On the other hand, defect emission intensity obtained upon 543 nm excitation increases significantly at elevated temperatures. The opposite thermal monotonicity of these two signals in the same spectral range enabled development of the single band ratiometric luminescent thermometer of as high a relative sensitivity as 4.92%/°C and 2%/°C for Y2O3:Tb3+ and Lu2O3:Tb3+ nanocrystals, respectively. This study presents the first report on luminescent thermometry using defect emission in inorganic phosphors.

Tuneable emission of Ba2Ca1-xMx(PO4)2:Eu2+ (M=Mg, Sr, Mg–Sr, and Zn) by multi-cation substitution: Selective excitation, thermal back-transfer, and applications

A series of tuneable emission phosphors Ba2Ca1-xMx(PO4)2:Eu2+ (M = Mg, Sr, Mg–Sr, and Zn) was prepared using multi-cation substitution. A new mechanism of direct/indirect substitution of Eu2+ for a host containing more than one cation and a concept of “selective excitation” for a multiple luminescence centres are proposed that are of great significance for analysing the changes of spectra and for designing colour tuneable phosphors. The emission spectra show a red shift (479 → 602 nm) with colour tuning from blue to yellow in Ba2Ca1-xMgx(PO4)2:Eu2+ and a blue shift (485 → 441 nm) in Ba2Ca1-xSrx(PO4)2:Eu2+. For Ba2Ca1-xZnx(PO4)2:Eu2+, the emission peak first turns from 494 to 442 nm and then a red shift occurs from 442 to 585 nm when excited at 355 nm, while a continuous red shift was observed under excitation of 400 nm. Three different patterns (solid solution material, mixture transition state, and new host component) of phosphors were presented when many foreign cations were introduced into the original host. The energy transfer and thermal back-transfer over the barrier were demonstrated in as-prepared samples. Warm white light-emitting diodes (LEDs) with the International Commission on Illumination (CIE) chromaticity coordinates of (0.3622 and 0.3051), a colour rendering index (Ra) of 88.7, and a correlated colour temperature (CCT) of 3947 were realised using as-prepared phosphors. The as-developed compound series has the potential for further optimisation for commercial applications in daylight LEDs and warm white LEDs.

Evaluating the Impact of Future Global Climate Change and Bioeconomy Scenarios on Ecosystem Services Using a Strategic Forest Management Decision Support System

Sustainable Forest Management (SFM) has become an important pillar of modern forest management, and one way to evaluate the sustainability of forestry is to assess long-term supply of ecosystem services (ESs) indicators. The concept of sustainability also has come to include adapting to climate change and the associated dynamic timber markets. This study aims to: 1) incorporate several ESs indicators in a Forest Management Decision Support System (FMDSS) that can deal with climate change and dynamic timber markets; and 2) analyse the impact that intensified forest management, resulting from global change scenarios that represent different levels of climate change mitigation efforts, will have on forest ES indicators in the west of Ireland. A linear programming model that optimized Net Present Value (NPV) from mill-gate sales was previously developed in Remsoft Woodstock, a DSS framework used for strategic forest planning around the world. This Woodstock model was modified to include the effects of global scenarios that include climate change and dynamic timber prices. This model was further developed to include indicators for five ESs (carbon storage in the forest as well as in harvested wood products and carbon substitution, windthrow risk, biodiversity, water quality, and cultural values), to assess the impacts of these global scenarios on the forest landscape and the sustainability of forest management. The ES indicator values were mainly linked to forest age, forest type, and yield tables, and their inclusion in the FMDSS had almost no impact on total model run times. Intensified forest clearfelling, as a result of increasing timber prices associated with most global scenarios, led to increased phosphor emissions to waterbodies, and reductions in windthrow risk and carbon storage. The global scenarios only resulted in minor differences in the indicator values for biodiversity and cultural values. Besides the global scenarios, recent forest policy development and the poor soil conditions in the study area impacted on the results. The developed system, with its innovative method to incorporate climate change and associated market dynamics, could be applied to other forest landscapes in Ireland and Europe, or indeed by any forest company or organisation that uses Remsoft Woodstock.

A novel narrow-band blue-emitting phosphor of Bi3+-activated Sr3Lu2Ge3O12 based on a highly symmetrical crystal structure used for WLEDs and FEDs

Investigating highly efficient narrow-band emission phosphors that have strong excitation bands in the near-ultraviolet (NUV) region is the main goal of the present light-emitting diode (LED) research, especially for Bi3+-activated phosphors. The naked 6s and 6p electrons of Bi3+ are sensitive to the microenvironment, thus leading to broad emission bands, while most Bi3+-activated phosphors suffer from low absorption of NUV-LED chips. Here, we report on a narrow-band blue-emitting garnet-type phosphor of Sr3Lu2Ge3O12: Bi3+ that is available for NUV-LED chips; its full width of the half maximum (FWHM) is limited to 40 nm, which is comparative to rare earth-activated phosphors, such as commercial blue phosphor BaMgAl10O17: Eu2+ (FWHM ≈ 52 nm), and this phenomenon is extremely rare among most Bi3+-activated phosphors. The internal quantum efficiency (IQE) of Sr3Lu2Ge3O12: Bi3+ can reach 57%. Moreover, it is interesting to find that Sr3Lu2Ge3O12: Bi3+ also exhibits exalting cathodoluminescence properties and its narrow-band emission produces brilliant images with high color saturation. The significant luminescent properties of trivalent bismuth are ascribed to the compact and highly symmetrical crystal structure of Sr3Lu2Ge3O12; thus, the discussion of the structure-property relations for Bi3+-activated Sr3Lu2Ge3O12 is the most anticipated part of this work. The results pave the way for the design of better Bi3+-activated phosphors for use as white light emitting diodes (WLEDs) and field emission displays (FEDs).

A dual-excited emission phosphor Eu3+/Eu2+ co-doped Ca4Si2O7F2: Lattice occupancy and luminescence characterization

A novel adjustable dual excited emission Eu2+/Eu3+ co-doped Ca4Si2O7F2 phosphor are reported. Unlike most of Eu2+ doped inorganic compounds, in the host lattice Ca4Si2O7F2, partial Eu3+ can still exist stably even in reducing atmosphere. The adjustable dual excited emission from blue light to red light can be found by changing the wavelength of excitation emission or the concentration of europium doped ion. The mechanism by which the two ions Eu2+ and Eu3+ can coexist in Ca4Si2O7F2 is revealed through the bond energy theory. Eu2+ and Eu3+ in Ca4Si2O7F2 system can be demonstrated to occupy the Ca1 lattice of Ca4Si2O7F2.