Energy transfer and photoluminescent analysis of a novel color-tunable Ba2Y1-xV3O11:xSm3+ nanophosphor for single-phased phosphor-converted white LEDs

Metal nitrates are used to synthesize a series of novel Ba₂Y_1-xV₃O₁₁:xSm³⁺ nanophosphors via urea-assisted solution combustion route. X-ray diffraction (XRD), diffuse reflectance (DR), transmission electron microscopy (TEM) and photoluminescence (PL) spectroscopy were employed to analyse the structure, morphology, photoluminescent behaviour and energy transfer mechanism. Rietveld analysis over Ba₂Y_0.98Sm_0.02V₃O₁₁ showed that Y³⁺ ions can be well-replaced by trivalent samarium ions without resulting any major alteration in the crystal structure of host lattice. Furthermore, the lattice parameters were determined for both the host as well as the doped composition. The Scherrer equation yielded an average particle size of 44?nm, which in turn was further confirmed by TEM micrographs. The optical band-gap of the host (3.92?eV) was calculated from the diffuse reflectance spectra. Moreover, the photoluminescence spectral studies showed that under near ultra-violet (NUV) excitation of 340?nm, our nanophosphor powder exhibits the characteristic emission peaks of trivalent samarium along with the emission of VO₄^3? (501?nm) group. The excitation energy transfer from vanadate group to Sm³⁺ produced a systematic color tunablity in white region itself. The optimum Sm³⁺ concentration for better luminescence was found to be 2?mol%. The critical distance for energy transfer was calculated to be 29.02?Å, which in turn assisted to shortlist the mechanism responsible for luminescence-quenching (dipole-dipole) arising from the over-doping of the activator. The photoluminescence decay curves revealed the decay kinetics of ⁴G_5/2 electronic state. Finally, the calculation of CIE color coordinates from emission spectra in MATLAB program unveiled a somewhat white-light emitter which may find potential applications in phosphor-converted white light emitting diodes (PC-WLED) under near-ultraviolet (NUV) excitation.     

Effects of argon sintering atmosphere on luminescence characteristics of Ca6BaP4O17:Sm3+ phosphors

In this paper, Ca₆BaP₄O₁₇:Sm³⁺ and Li⁺ co-doped Ca₆BaP₄O₁₇:Sm³⁺ phosphors were synthesized in air and argon atmospheres using a solid-state reaction method. The phosphor morphologies and crystal structure were studied using scanning electron microscopy and X-ray diffraction, respectively. The emission and absorption characteristics were investigated using photoluminescence emission spectroscopy and diffuse reflectance spectroscopy. The surface states and composition of phosphor were investigated using X-ray photoelectron spectroscopy. The emission integrated intensities of the phosphors sintered in an argon atmosphere increased 3.5 fold than the ones sintered in air atmosphere, with Li⁺ ions becoming embedded in the lattice of the Ca₆BaP₄O₁₇:Sm³⁺ phosphor. This occurs because there are fewer defect/oxygen vacancies and less of the secondary phase forms, leading to better Sm³⁺ emission. The results suggest that sintering a mixture of the raw materials of a phosphor in an argon atmosphere is a good approach for synthesizing Ca₆BaP₄O₁₇:Sm³⁺ phosphor powders. The color purity and CIE values of an optimized phosphor sample sintered in an argon atmosphere with an Li⁺ ion compensator were calculated to be ~ 99.6% and (0.612,0.386) in the orange–red region under 405-nm excitation, respectively. Moreover, the solid solubility of Sm³⁺ ions in the Ca₆BaP₄O₁₇ host can be enhanced by using an argon atmosphere in the synthesis process.     

Photoluminescence and optical temperature sensing in Sm3+-doped Ba0.85Ca0.15Ti0.90Zr0.10O3 lead-free ceramics

A series of orange-red emitting Sm³⁺ activated Ba_0.85Ca_0.15Ti_0.90Zr_0.10O₃ (BCZT: xSm³⁺, x?=?0.001–0.007) are synthesized by a conventional solid-state reaction method. The Sm³⁺ ions composition dependent photoluminescence properties are systematically investigated. Under the excitation of a 407?nm near-ultraviolet light, the ceramics exhibit strong characteristic emission of Sm³⁺ ions with dominant orange-red emission peak at around 595?nm, which is ascribed to the transition of ⁴G_5/2 → ⁶H_7/2. The BCZT: 0.004Sm³⁺ ceramic displays the optimal emission among these Sm³⁺-doped BCZT solid solutions. Moreover, the photoluminescence intensity exhibits extremely sensitive to temperature, suggesting that BCZT: 0.004Sm³⁺ could be applicable for temperature sensing. A maximum relative sensitivity of 1.89%?K^?1 at 453?K is obtained. Furthermore, the existence of ferroelectricity in the BCZT host combined with Sm³⁺ activated photoluminescence properties could be useful for developing optical-electro multifunctional materials and devices.     

Photoluminescence and electron-beam excitation induced cathodoluminescence properties of novel green-emitting Ba4La6O(SiO4)6:Tb3+phosphors

Tb³⁺ions activated Ba₄La₆O(SiO₄)₆ (BLSO:Tb³⁺) phosphors were synthesized by a citrate sol-gel method. The X-ray diffraction pattern confirmed their oxyapatite structure. The field-emission scanning electron microscope image established that the BLSO:Tb³⁺phosphor particles were closely-packed and acquired irregular shapes. The photoluminescence (PL) excitation spectra of BLSO:Tb³⁺phosphors showed intense f–d transitions along with low intense peaks corresponding to the f–f transitions of Tb³⁺ions in the lower energy region. The PL emission spectra displayed the characteristic emission bands of Tb³⁺ions, and the optimized concentrations were found to be at 1 and 6 mol% for blue and green emission peaks, respectively. The cathodoluminescece (CL) spectra exhibited a similar behavior that was observed in the PL spectra except the intensity variations in the blue and green regions. The CL spectra of the BLSO:6 mol% Tb³⁺phosphor unveiled accelerating voltage induced luminescent properties.     

Spectroscopic investigations on high efficiency deep red-emitting Ca2SiO4:Eu3+ phosphors synthesized from agricultural waste

Europium doped calcium orthosilicate (Ca₂SiO₄) phosphors have been synthesized by the conventional high temperature solid-state reaction method in various concentrations from agricultural waste (egg shell as a CaO and rice husk as a SiO₂). These phosphors structure from X-ray diffraction and morphology from scanning electron microscopy have been examined. Concentration dependent Eu³⁺ ions luminescent properties in Ca₂SiO₄ phosphors have been studied from the excitation, emission and decay curves analysis. The ⁵D₀ → ⁷F_J transitions observed in luminescence spectrum allows to determine the site symmetry of the Eu³⁺ ion. A charge transfer band (CTB) at around 260?nm which is due to the Eu–O interaction in the host along with the 4f – 4f excitation bands due to Eu³⁺ ions in UV and blue regions are observed. The color co-ordinates determined from emission spectra varies with concentrations of Eu³⁺ ions and are found to fall in the red region. The decay curves show single exponential behavior for all concentrations of Eu³⁺ ions (0.01–0.4?mol%) and the lifetimes varied from 2.67 to 2.78?ms. It is worth noting that the present material is found to be far better than many red phosphors synthesized by using agricultural waste as raw materials.     

Color-tunable properties based on complex anion substitution in Eu2+ doped Ca8Sc2(PO4)6-y(SiO4)1+y phosphor

We synthesized and investigated the effect of Eu²⁺ ions doping in a novel phosphor-silicate Ca₈Sc₂(PO₄)₆(SiO₄) phosphor. The structure and photoluminescence properties were determined by X-ray powder diffraction Rietveld refinement, diffuse reflection spectra, emission-excitation spectra, decay curves and temperature dependence spectra. The phosphors showed an asymmetric broad-band blue emission (Eu²⁺) with peak at 470?nm. Furthermore, we presented the Ca_7.96Sc₂(PO₄)_6-y(SiO₄)_1+y:0.04Eu²⁺ phosphors by co-substituting [Eu²⁺-Si⁴⁺] for [Ca²⁺-P⁵⁺], and different behaviors of luminescence evolution in response to structural variation were verified among the series of phosphors. The results were attributed to the presence of multi Ca²⁺ sites, resulting in the mixing of blue and green emissions for Eu²⁺ ions. The complex anion substitution of [PO₄]^3- by [SiO₄]^4- induced an increased crystal field splitting of the Eu²⁺ ions, which caused a decrease in emission energy from the 5d excited state to the 4f ground state and a resultant red-shift from 470?nm to 520?nm. All the properties indicated that the Ca₈Sc₂(PO₄)₆(SiO₄):Eu²⁺ phosphors have potential application for color-tunable WLEDs.     

A New Blue‐Emitting Phosphor of Ce3+‐Activated Fluorosilicate Apatite Ba2Y3[SiO4]3F

Blue‐emitting phosphor of Ce³⁺‐activated fluorosilicate apatite Ba₂Y₃[SiO₄]₃F was prepared via conventional solid‐state reaction method. The X‐ray powder diffraction (XRD), scanning electron microscopy (SEM), photoluminescence (PL) excitation and emission spectra, and the decay curves (lifetimes) were applied to characterize the phosphors. The effects of Ce³⁺ activator concentration on the luminescence properties were investigated. Ba₂Y_2.85Ce_0.15[SiO₄]₃F exhibits the brightest blue emission with CIE coordinates of (x = 0.231, y = 0.301). The crystallographic site of Ce³⁺ ions in Ba₂Y₃[SiO₄]₃F lattices was identified. Two kinds of crystallographic Ce³⁺ occupying MI and MII sites in Ba₂Y₃[SiO₄]₃F lattices result in two distinct emission centers. The internal PL quantum efficiency, the temperature‐dependent luminescence, and the activation energy of thermal quenching were investigated to evaluate the potential application. This is a new kind of blue‐emitting phosphor based on apatite structure.     

Improvement of photoluminescence properties of Ce3+- doped CaSrAl2SiO7 phosphors by charge compensation with Li+ and Na+

In this work, we prepared CaSr_1-xAl₂SiO₇:xCe³⁺ (0.03 ≤ x ≤ 0.12) and CaSr_0.94Al₂SiO₇:0.03Ce³⁺,0.03 M⁺ (M⁺ = Li⁺ and Na⁺) phosphors via solid-state reaction method. Structural and photoluminescence (PL) properties of the phosphors were also investigated. The prepared phosphors formed an orthorhombic crystal structure with the P2₁2₁2₁ space group. CaSr_1-xAl₂SiO₇:xCe³⁺ phosphors were effectively excited by near-ultraviolet (UV) light (345 nm), which is suitable with the emission of near-UV light emitting diode chips. A broad blue emission (402 nm) was detected in CaSr_1-xAl₂SiO₇:xCe³⁺ and CaSr_0.94Al₂SiO₇:0.03Ce³⁺,0.03 M⁺ phosphors; this was attributed to the 4f⁰5d¹ → 4f¹ transition of Ce³⁺. To maintain charge equilibrium, charge compensators, such as monovalent Li⁺ and Na⁺ ions, were doped into the CaSr_0.97Al₂SiO₇:0.03Ce³⁺ phosphor, significantly improving its PL properties. The strongest emission intensity was achieved in CaSr_0.94Al₂SiO₇:0.03Ce³⁺,0.03Li⁺ phosphor. Addition of Li⁺ charge compensator was highly effective in improving PL properties of CaSr_0.97Al₂SiO₇:0.03Ce³⁺ phosphors.     

Luminescence properties of Eu activated Ba2Si5N8 red phosphors with various Eu contents

This study was carried out to characterize the crystal structure and luminescence properties of Eu²⁺ doped red-emitting Ba₂Si₅N₈ phosphor. In this research, Ba₂Si₅N₈ phosphors with various Eu compositions were prepared by normal pressure sintering (NPS). Ba₃N₂, Si₃N₄ and Eu₂O₃ were sintered at a high temperature in a mixture of N₂ and H₂. The crystal structure was analyzed by X-ray diffraction(XRD), and the photoluminescence(PL) properties of the Eu²⁺ - activated Ba₂Si₅N₈ phosphors were evaluated as a function of the Eu²⁺ activator concentration. The red-emitting Ba₂Si₅N₈ phosphors showed a broad excitation band range as well as high quantum output.     

Preparation of Sr2SiO4:Eu phosphors by microwave-assisted sintering and their luminescent properties

An Eu³⁺ activated strontium silicate phosphor was synthesized using a microwave-assisted sintering with a flux NH₄Cl. X-ray powder diffraction analysis confirmed the formation of pure Sr₂SiO₄ phase without second phase or phases of starting materials as Sr_1.9SiO₄:Eu³⁺_0.1 powders sintered at various temperatures in microwave furnace for 1 h. Scanning electron microscopy showed smaller particle size and more uniform grain size distributions are obtained by microwave-assisted sintering. In the PL studies, the excitation spectrum of Sr_1.9SiO₄:Eu³⁺_0.1 phosphors exhibited a broad band in the UV region centered at about 270 nm which was consistent with the absorption spectra. Both microwave sintered and conventionally sintered powders emitted a maximum luminescence centered at 617 nm under excitation of 395 nm, with similar luminescent intensity. The results showed that microwave processing has the potential to decrease the sintering time and required energy input for the production of Sr_1.9SiO₄:Eu³⁺_0.1 phosphors without degrading photoluminescence.     

Red-emitting enhancement of Bi4Si3O12:Sm3+ phosphor by Pr3+ co-doping for White LEDs application

In this account, Bi₄Si₃O₁₂:Sm³⁺ and (Bi₄Si₃O₁₂:Sm³⁺, Pr³⁺) red phosphors were prepared by solution combustion method fueled by citric acid at 900 °C for 1 h. The effects of co-doping Pr³⁺ ions on red emission properties of Bi₄Si₃O₁₂:Sm³⁺ phosphors, as well as the mechanism of interaction between Sm³⁺ and Pr³⁺ ions were investigated by various methods. X-ray diffraction (XRD) and Scanning electron microscopy (SEM) revealed that smaller amounts of doped rare earth ions did not change the crystal structure and particle morphology of the phosphors. The photoluminescence spectroscopy (PL) indicated that shape and position of the emission peaks of (Bi₄Si₃O₁₂:Sm³⁺, Pr³⁺) phosphors excited at λ_ex=403 nm were similar to those of Bi₄Si₃O₁₂:Sm³⁺ phosphors. The strongest emission peak was recorded at 607 nm, which was attributed to the ⁴G_5/2→⁶H_7/2 transition of the Sm³⁺ ion. The photoluminescence intensities of Bi₄Si₃O₁₂:Sm³⁺ phosphors were significantly improved by co-doping with Pr³⁺ ions and were maximized at Sm³⁺ and Pr³⁺ ions doping concentrations of 4 mol% and 0.1 mol%, respectively. The characteristic peaks of Sm³⁺ ions were displayed in the emission spectra of (Bi₄Si₃O₁₂:Sm³⁺, Pr³⁺) phosphors excited at respectively λ_ex=443 nm and λ_ex=481 nm (Pr:³H₄→³P₂, ³H₄→³P₀). This indicated the existence of Pr³⁺→Sm³⁺ energy transfer in (Bi₄Si₃O₁₂:Sm³⁺, Pr³⁺) phosphors.     

Luminescence and structure of Eu2+-doped Ba2CaMg2Si6O17

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.     

Potential red-emitting NaGd(MO4)2:R (M=W,Mo, R=Eu,Sm, Bi) phosphors for white light emitting diodes applications

NaGd(MO₄)₂:R (M=W, Mo, R=Eu³⁺, Sm³⁺, Bi³⁺) phosphors were synthesized by solid-state reaction. The structure and photoluminescence properties of the samples were characterized using X-ray powder diffraction and fluorescence spectrophotometry. The ⁵D₀→⁷F₂ transition of Eu³⁺, which led to a red emission of the phosphors, was dominantly observed in the photoluminescence spectra. The doped Bi³⁺ and Sm³⁺ efficiently sensitized the emission of Eu³⁺ and effectively extended and strengthened the absorption of near-UV light with wavelengths ranging from 395 to 405 nm. In addition, energy transfers from Bi³⁺ to Eu³⁺ and from Sm³⁺ to Eu³⁺ occurred. The chromaticity coordinates of the obtained phosphors were close to the standard values of the National Television Standard Committee (x=0.670, y=0.330). The results suggest that NaGd(WO₄)_2−y(MoO₄)_y:Eu³⁺, Sm³⁺, Bi³⁺ is an efficient red-emitting phosphor for light-emitting diode applications.     

Cyan-emitting Ba0.45Ca2.5La6(SiO4)6: 0.05 Eu2+ and Ba1.45Ca1.5La6(SiO4)6:0.05 Eu2+ solid-solution phosphors for white light-emitting diodes

Two cyan-emitting phosphors with different bandwidths were successfully synthesized through the high-temperature solid-state method in a reducing atmosphere. The crystal structures, morphologies, and luminescence properties of the as-prepared phosphors were investigated. The Rietveld refinements of the powder X-ray diffraction (XRD) data demonstrated the single phase of the samples, and two crystallographic sites of La³⁺ were observed in the crystal structure. Under the excitation of UV light, both Ba_0.45Ca_2.5La₆(SiO₄)₆: 0.05 Eu²⁺ and Ba_1.45Ca_1.5La₆(SiO₄)₆: 0.05 Eu²⁺ phosphors emitted cyan light due to the 4f⁶5 d¹→4f⁷ transitions of the Eu²⁺ ion. The emission spectra could be well fitted by two component Gaussian peaks corresponding to two different coordination environments of the Eu²⁺ ions. The temperature-dependent photoluminescence spectra show a large difference on the thermal stability between the two phosphors. The two phosphors exhibit effective absorption of near-UV light and their internal quantum efficiencies (IQEs) were calculated as 31.5% and 42.4% under 295 nm UV-light excitation. The experimental results indicate that the novel cyan phosphors might have potential applications in white light-emitting diodes (LEDs) based on the near-UV LED chip.     

White‐emitting phosphor Ba2B2O5:Ce3+, Tb3+, Sm3+: Luminescence,energy transfer,and thermal stability

A series of Ba₂B₂O₅: RE (RE=Ce³⁺/Tb³⁺/Sm³⁺) phosphors were synthesized using high‐temperature solid‐state reaction. The X‐ray diffraction (XRD), luminescent properties, and decay lifetimes are utilized to characterize the properties of the phosphors. The obtained phosphors can emit blue, green, and orange‐red light when single‐doped Ce³⁺, Tb³⁺, and Sm³⁺. The energy can transfer from Ce³⁺ to Tb³⁺ and Tb³⁺ to Sm³⁺ in Ba₂B₂O₅, but not from Ce³⁺ to Sm³⁺ in Ce³⁺ and Sm³⁺ codoped in Ba₂B₂O₅. However, the energy can transfer from Ce³⁺ to Sm³⁺ through the bridge role of Tb³⁺. We obtain white emission based on energy transfer of Ce³⁺→Tb³⁺→Sm³⁺ ions. These results reveal that Ce³⁺/Tb³⁺/Sm³⁺ can interact with each other in Ba₂B₂O₅, and Ba₂B₂O₅ may be a potential candidate host for white‐light‐emitting phosphors.     

Biocompatibility and photoluminescence of Sm3+-doped SiO2-Gd2O3: A promising non-toxic red phosphor to plasmatic membrane tracking

Sm³⁺ doped SiO₂-Gd₂O₃ composites were obtained by a sol-gel process, and the ideal percentage of Sm³⁺ was evaluated for bioimaging applications. By XRD, a formation of Gd₂O₃ cubic materials was observed, and TEM shows that Gd₂O₃ particles are dispersed in a SiO₂ lattice. PLE spectra confirm the main absorption bands in the UV region and emission shows the most efficient excitation at 275 nm. PL results reveal the incorporation of Sm³⁺ in Gd₂O₃ structures and lead to the understanding of the efficient energy transfer between Gd³⁺ and Sm³⁺ in the materials. The mechanism is proposed and discussed. CIE plotting shows color coordinates in the orange and red regions, mainly dependent on the excitation source. Sm³⁺ positions in Gd₂O₃ are discussed using the results obtained in the emission spectra. Materials presented high lifetime values, between 1.53 and 1.82 ms. The phosphors show tunability properties and better performance as red phosphors when excited at 275 nm. Cell viability was performed and the material is non-toxic. The materials were evaluated as biological markers, and present fluorescence under rhodamine emission filters. SiO₂-Gd₂O₃:Sm³⁺ demonstrates a good viability index and co-localizes with membrane cell markers, showing a promising material for cell tracking. The material also demonstrates potential for cancer targeting.     

Synthesis and spectroscopic analysis of Sm3+ doped CeO2 ceramic powders for the application of white LEDs

Orange-red light-emitting Sm³⁺-doped cerium oxide (CeO₂) ceramic powder with various concentrations of Sm³⁺ ions was prepared through a sol-gel process. X-ray diffraction and Rietveld analysis confirmed the formation of a purely cubic structure with a space group of $\mathit{Fm}\stackrel{?}{3}m$. The lattice parameters and unit cell volumes of the CeO₂:Sm³⁺ powder increased with the concentration of Sm³⁺ ions. The energy-dispersive X-ray spectra and corresponding mapping images confirmed the elemental composition and adequate dispersion of all elements in the CeO₂:Sm³⁺ powder. A broad excitation band at approximately 365?nm was observed in the excitation spectra of CeO₂:Sm³⁺ phosphors owing to the charge transfer transition from O 2p to Ce 4f orbitals. The Sm³⁺ doped CeO₂ phosphors emitted sharp luminescence with a main peak at 615?nm under excitation at 360?nm. The spectral analysis revealed that the CeO₂:Sm³⁺ phosphors exhibited strong orange-red emission. Concentration quenching was observed in the CeO₂:Sm³⁺ phosphors with 0.5?mol% of critical concentration of Sm³⁺ ions due to dipole dipole interaction of two nearest Sm³⁺ ions. The quantum efficiency was observed as high as 58%. The thermal stability of the present materials was estimated with the evaluation of activation energy as 0.31?eV. The broad excitation band and sharp orange–red emission indicated the potential use of CeO₂:Sm³⁺ phosphors for white light-emitting diodes.     

X-ray photoelectron spectroscopy and optical analysis of pure white light emitting Dy3+ and Mn2+ codoped Na3Y(PO4)2 phosphors for solid-state lighting

A single-phase and optimized pure white light emitting Dy³⁺-doped and Dy³⁺/Mn²⁺ codoped Na₃Y(PO₄)₂ phosphors (NYPO) were synthesized by traditional solid state reaction process. The as-synthesized phosphors were characterized by X-ray diffraction, X-ray photoelectron spectroscopy (XPS), diffuse reflectance spectra and photoluminescence studies. The results suggested that the NYPO: Dy, Mn phosphors were crystallized in orthorhombic structures. The presence of dopants Dy and Mn was quantified by XPS analysis. All of the phosphors were effectively excited using a light of wavelength 351?nm and emissions in two regions, blue (~482?nm, ⁴F_9/2→⁶H_15/2) and yellow (~573?nm, ⁴F_9/2→⁶H_13/2), were obtained due to the f-f transitions of Dy³⁺ ions. The maximum intensities of Dy and Mn obtained were 0.07 and 0.05 for NYPO:Dy and NYPO:0.07Dy, Mn, respectively. The chromaticity coordinates, color temperatures, and color rendering indices of NYPO: 0.07Dy ((0.32, 0.33), 6194?K, and 48) and NYPO:0.07Dy, 0.05Mn phosphors ((0.33, 0.33), 5688?K, and 62) were determined. The energy transfer mechanism and oxygen vacancies that arise due to the introduction of Mn²⁺ ions in the NYPO:Dy phosphors, are responsible for the tuning of cool white light to pure day white light. The introduction of Mn in the Dy doped NYPO phosphor enhances the emission intensity in the phosphor.     

Spectroscopic characterizations and investigation of Judd-Ofelt intensity parameters of Dy3+-doped Ba2La8(SiO4)6O2 near white light emitting phosphor

A series of Dy³⁺-activated Ba₂La₈(SiO₄)₆O₂ phosphors were synthesized using the solid-state method with the objective of developing single host white light emitting phosphors for use in solid state lighting applications. The Dy³⁺ concentration varied between 0.01 and 0.05 mol%. The as-prepared phosphors crystal structure, optical, and photoluminescent properties (PL), along with energy transfer mechanism and luminescence decay, were investigated. The production of a single-phase Ba₂La₈(SiO₄)₆O₂ with hexagonal symmetry was verified by the findings of the X-ray diffraction analysis. When the Ba₂La₈(SiO₄)₆O₂: Dy³⁺ phosphors are exposed to ultraviolet light, they emit the characteristic yellow PL emissions caused by the ⁴F_9/2 → ⁶H_13/2 transition. The Judd-Ofelt (J-O) parameters (Ω₂, Ω₄, Ω₆) were computed using the excitation spectra. The characteristics of the Dy³⁺ transition indicate that the asymmetric environment around the ligand was suggested by the trend, which was followed by J-O parameters. Due to the dominance of the electric-dipole transition in the luminescence spectrum, the Ba₂La₈(SiO₄)₆O₂:0.03Dy³⁺ phosphor displayed yellowish white emission with CIE coordinates of (0.358, 0.398) and a CCT of 4724 K. The synthesized phosphor may be a useful material in the fabrication of white-emitting phosphor for LEDs application.     

White light emission from Eu co-activated Ca2Gd8Si6O26:Dy nanophosphors by solvothermalsynthesis

Ca₂Gd₈(SiO₄)₆O₂ (CGS) nanophosphors with different concentrations of single-doped Dy³⁺ ions and co-doped Dy³⁺/Eu³⁺ ions were prepared by a solvothermal synthesis. Very fine particles in the nanometer range could be achieved by this method, as evidenced by transmission electron microscope measurements. The hexagonal phase of the oxyapatite structure was confirmed by X-ray diffraction patterns. The energy transfer between Eu³⁺ and Dy³⁺ ions was investigated by photoluminescence excitation and emission properties. These phosphors had absorption bands in the UV and NUV region, which are suitable for the emission wavelength of UV or NUV light-emitting diodes (LEDs). With increasing the Eu³⁺ ion concentration, the emission peak intensity corresponding to the ⁵D₀→⁷F₂ transition increased and the yellow (⁴F_9/2→⁶H_13/2) emission intensity also increased compared to the blue (⁴F_9/2→⁶H_15/2) emission intensity due to the increased energy transfer between Dy³⁺ to Eu³⁺ ions. Thus, the Eu³⁺ ions compensated the red emission component of the Dy³⁺ doped CGS nanophosphors. Such phosphors are expected to have potential applications for NUV based white LEDs.