Single-phased Phosphor Research Articles

Synthesis and luminescence properties of Eu3+, Dy3+ co-doped Ca3Bi(PO4)3 single-phase phosphor

Synthesis and luminescence properties of Eu3+, Dy3+ co-doped Ca3Bi(PO4)3 single-phase phosphor

White-light emission from yttrium iron garnet (YIG)

Single-phase phosphors that emit broadband white-light are needed for white-light-emitting diodes (wLEDs) to reach their full potential. However, it is challenging to achieve broad white-light emission from single-phase materials. Consequently, polycrystalline inorganic bulk compounds that emit white-light sans doping are rare. We report on broadband white-light emission from a well-known garnet compound, i.e., yttrium iron garnet (YIG), without activator-ion doping. Upon near-UV excitation at 370 nm, polycrystalline bulk YIG emits broadband white-light with (1931) Commission Internationale de L’Eclairage (CIE) coordinates as (0.28, 0.35) and correlated color temperature (CCT) as 8029 K. Variable excitation wavelengths ranging from 280 to 600 nm enable color-tunable emission as cyan-white-blue-green-yellow-orange-red, including near-white-light emission for a broad range of excitation from 325 to 390 nm. Moreover, a short lifetime (sub-nanosecond) is obtained, which is desirable for LED and other applications. We demonstrated the propriety of YIG as a single-phase converting phosphor for illumination by fabricating prototype wLEDs using commercial InGaN UV-LED chips (λ = 380 nm) for excitation. The CIE coordinates and CCT of prototype wLEDs were obtained as (0.34, 0.37) and 5284 K, respectively. We believe that the reported findings signify the great potential of YIG as a single-phase white-light-emitting phosphor for broadband emission, which offers a new perspective and a viable approach for the development of wLEDs.

Strategic Tuning of Photophysical Response in the Polyhedral Framework of the Garnet Structure toward White Light-Emitting Devices with Enhanced Color Rendering.

Designing a single-phase phosphor with high quantum efficiency and full spectrum emission is inevitable for today's scientific world. Herein, an optimal strategy for realizing white emission in a single component matrix is envisaged based on the structure-property-design-device policy. Cationic substitution corresponding to polyhedral expansion and contraction in A2A'B2V3O12 confirms the existence of strong and intricate linkage in the garnet structure. The dodecahedral expansion causes compression of VO4 tetrahedra and a blue shift. The direct correlation of V-O bond distance with red shift validates the distortion of the VO4 tetrahedra. The interdependence of photophysical properties via cationic substitution and subsequent correlation of the V-O bond distance with emission bands enabled the tailoring of phosphor-CaSrNaMg2V3O12 with a high quantum efficiency of 52% and excellent thermal stability of 0.39 eV. Bright warm white light-emitting diode (WLED) devices are fabricated based on Eu3+ and Sm3+-activators. A high quantum efficiency-74% is obtained for the designed Eu3+ phosphor. CIE coordinates near the achromatic point (0.329, 0.366), low CCT-5623 K, and high color rendering index (CRI)-87 are obtained for the single-phase WLED device. This work puts forth a new direction for designing and engineering promising WLEDs with enhanced color rendering based on single-phase phosphors with full spectrum emission.

A novel yellow-emitting CaGdSbWO8:Dy3+ single-phase phosphor with high thermal stability and application in w-LEDs

A novel yellow-emitting CaGdSbWO8:Dy3+ single-phase phosphor with high thermal stability and application in w-LEDs

Structure and luminescence properties of single-component melilite Sr2MgSi2O7:Ce/Tb/Sm for n-UV wLEDs.

Phosphor-converted white light-emitting diodes (pc-wLEDs) have attracted attention in the field of solid-state lighting. Selection and study of suitable single-phase phosphor and packaging modes are currently the main research hotspots. Herein, color-tunable photoluminescence (PL) and thermally stable tri-doped Melitite Sr2MgSi2O7:Ce/Tb/Sm are systematically studied via structural and static/dynamic spectral analyses. All dopants could only be accommodated in the Sr site due to similar ionic radii. Previous studies have concluded that green and red PL could be obtained from singly doped Tb and Sm phosphors with excellent reproduction, and color tunable PL can be achieved from Ce/Tb co-doped phosphors. The forbidden 4f-4f transitions of Tb/Sm cause low efficiency and Ce/Tb co-doping cannot achieve white light emissions. Alternatively, co-doping allowed 5d-4f transition sensitizer with emissions in the UV-blue region (i.e., Ce), color-tunable PL (including the white light); high efficiency of Sr2MgSi2O7:Ce/Tb/Sm could be achieved via energy transfer (ET) from Ce → Tb → Sm. The impossibly direct ET from Ce → Sm is associated with the side metal-metal charge transfer (MMCT) effect. Due to chemically nonequivalent substitutions, two positive Ce(Tb,Sm)Sr and one negative V''Sr were created to maintain the whole charge balance. To reduce the defects and allow more dopants to enter into the Sr site, Na+ was added as a charge balancer to enhance PL efficiency. Furthermore, an alkaline-earth-metal-ions blending strategy via partial replacement of Sr with Ba was investigated to regulate PL owing to the change in crystal field splitting. PL blue-shifted by Ba-co-doping, which could increase the degree of overlapping and enhance ET efficiency. As a proof-of-concept experiment, the pc-wLED fabricated via a combination of the optimal Sr(Ba)2MgSi2O7:Ce/Tb/Sm/Na and an n-UV LED chip based on a remote 'capping' packaging mode shows excellent performances, indicating its strong potential application in the field of solid-state lighting.

Investigation of the luminescence properties and energy transfer mechanisms in Gd3TaO7:Bi3+,Eu3+ phosphors for their potential application in full-spectrum WLEDs.

In recent years, there has been increasing effort devoted to the development of single-phase white phosphors due to drawbacks such as severe reabsorption and color deviation in traditional white light-emitting diodes (WLEDs). A new feasible strategy has emerged for achieving white light emission through the Bi3+-Eu3+ energy transfer in suitable single-phase phosphors. Therefore, a series of Gd3TaO7:xBi3+ and Gd3TaO7:0.01Bi3+,yEu3+ phosphors were synthesized via a high-temperature solid-state method, and their properties were systematically characterized. In Gd3TaO7, Bi3+ occupies two kinds of Gd3+ site, resulting in two broad emission bands peaking at 427 nm and 500 nm respectively under ultraviolet (UV) excitation, which arise from 3P1 → 1S0 transitions. By adjusting the concentration of Eu3+ in Gd3TaO7:0.01Bi3+,yEu3+, effective energy transfer can occur between Bi3+ and Eu3+, thus enabling the regulation of green-white-red luminescence under 332 nm excitation and blue-white-red luminescence under 365 nm UV light irradiation. Upon stimulation with a 365 nm UV chip, Gd3TaO7:0.01Bi3+,0.02Eu3+ emits white light with CIE coordinates of (0.3509, 0.3202), a color temperature of 4629 K, and an impressive color rendering index of 87.96. The above results indicate the potential of Gd3TaO7:0.01Bi3+,yEu3+ phosphor as a viable candidate for WLED applications.

Tuning the Red Emission to Instigate Intrinsic White-Light Emission in Single-Phase Phosphor with Excellent Color Rendering Index.

There is ever-growing interest to develop intrinsic white light emitting single-phase phosphors that have high CRI, devoid of bluish tinge, ease of synthesis and are scalable. Herein, manipulating vacuum pressure to instigate white light emission in Cu2+ -doped-ZnS phosphors is reported. The detailed X-ray diffraction and electron microscopy confirm the cubic phase of Cu2+ -doped-ZnS phosphor having agglomerated particles (∼130-150 nm). The incorporation of Cu2+ in the ZnS lattice is substantiated by the anti-Stokes shift of Raman peaks and shifting of XRD peaks to higher 2θ values. Upon increasing Cu2+ doping concentration, the resulted decrease in the FWHM of XRD peaks implies shrinkage of the ZnS lattice. Interestingly, by tailoring the excitation wavelength, the stoichiometry of dopant ion, and defect states by varying the vacuum pressure, the optimized ZSC-3 (3% Cu2+ -doped-ZnS) displays the origin of clear blue, green and red emission bands, consequently giving rise to white light emission (CIE values: 0.345:0398). The PLQY and average lifetime calculated for ZSC-3 are 5.98% and 1.5 ms, respectively. Such intense white light emission prompted to fabricate a prototype using a 310 nm UV LED. It exhibits high CRI (97) and warm CCT (4538 K), meeting highly desired values for a white light-emitting phosphor for different lighting and electroluminescence applications.

Study of structural and spectroscopic characteristics of novel color tunable yellowish-white Dy3+ doped Gd4Al2O9 nanophosphors for NUV-based WLEDs

Urea-assisted solution combustion (SC) synthetic method is employed to prepare a series of yellowish-white light emitting Dy3+doped Gd4Al2O9 (x = 1–6 mol%) phosphors. Phase identification and refinement parameters of designated nanomaterials are analyzed by means of Rietveld refinement technique. All doped samples are structured into monoclinic crystal system with P21c space group. Scherrer's formula and Williamson-Hall (W-H) linearly fitted method are employed to enumerate the crystallite size that are observed in the domain of nano-scale. The transmission spectrum of diffused reflectance is utilized to calculate the optical energy band gap of optimized sample Gd3.97Dy0.03Al2O9 that come out to be 5.11 eV. TEM micrograph discloses the existence of non-uniform agglomerated particles. The photophysical characteristics of doped phosphors are analyzed by exploiting their photoluminescence excitation (PLE) and emission profiles. The most intense excitation peak is found to be at 351 nm, which is meticulously harmonized with the distinctive wavelength of commercialized near ultra-violet (NUV) based LED chips. The emission profile of all doped samples possesses sharp emission lines centered at 481, 573, and 667 nm, which are ascribed to 4F9/2→6H15/2, 4F9/2→6H13/2, and 4F9/2→6H11/2 intraconfigurational transitions of Dy3+ ion, correspondingly. The emission decay curves are well fitted with bi-exponential function and in good agreement with findings of the refinement analysis viz. existence of two non-centrosymmetric sites attained by the Dy3+ ions. Auzel's model is used to estimate the radiative lifetime (τR= 5.14356 ± 0.65104 ms). The chromaticity coordinates and correlated color temperature (CCT) values for all doped samples are found close to standard white coordinates, thus proved them a potential candidate in single-phase phosphor converted WLEDs.

Microstructure and photoluminescence of Eu-doped Sr3Al2O6 phosphors calcined with and without H3BO3 flux

The development of highly efficient and stable red phosphors fabricated using cost-effective and simple mass-production methods is essential for applications in future displays and lighting devices. Herein, we investigate the phase formation, microstructures, and luminescence properties of Sr3Al2O6:Eu powders synthesized using a solid-state reaction process. Single-phase Sr3Al2O6:Eu phosphors exhibiting excellent photoluminescence with color-tunable orange-red and red colors under different excitation wavelengths were successfully synthesized. The optimal Eu doping concentration of Sr3Al2O6, yielding strong photoluminescence with phase stability, was 5 at. %, with the concentration quenching point determined by systematic exploration. The addition of H3BO3 as a flux significantly affected the grain size and improved the emission intensity of the synthesized (Sr0.95Eu0.05)3Al2O6 phosphors up to 12.5 wt %, while secondary phases were formed at higher flux concentrations. The photoluminescence intensities of the 5D0 → 7F1 and 5D0 → 7F2 transitions of 12.5 wt % H3BO3 added (Sr0.95Eu0.05)3Al2O6 increased by 3.4 and 4.2 times compared with the flux-free powders under the 394 nm-wavelength excitation, while the decay time decreased from 7.35 to 5.40 ms. Our report of the enhanced photoluminescence intensity and shortened decay time of (Sr0.95Eu0.05)3Al2O6 phosphors following the flux addition is promising for production of single-phase phosphors emitting multi-colors, which is needed for optical devices activated by various excitation frequencies.

Tunable photoluminescence of LiNbO3: RE3+ (RE3+ = Dy3+, Sm3+, Dy3+/Sm3+) single-phase phosphors for warm white LEDs

LiNbO3 single-phase phosphors with varying single-doping and co-doping contents of Dy3+ and Sm3+ ions were fabricated via the solid phase reaction. All the X-ray diffractions of these samples revealed that they belonged to the single-phase trigonal structure of LiNbO3. LiNbO3: Dy3+ phosphors could have a neutral white light at 392 nm excitation owing to two strong emission bands (at 488 and 585 nm). Upon the excitation of 412 nm, LiNbO3: Sm3+ phosphors produced orange-red light which attributed to the biggest emission of Sm3+ at 613 nm. The most appropriate doping content of Dy3+ and Sm3+ and the concentration quenching mechanism were also examined. The PL spectra of Dy3+ matched well with the PLE spectra of Sm3+, implying that the energy might be delivered from Dy3+ to Sm3+. At 392 nm excitation, Dy3+ and Sm3+ co-doping LiNbO3 phosphors showed tunable photoluminescence from ordinary to warm white light when doped with more Sm3+ ions. The process of Dy3+ passing on the energy to Sm3+ was validated through the PL spectra of LiNbO3: Dy3+/Sm3+ phosphors. The decay lifetimes also affirmed the energy transfer process. Moreover, Li0.97NbO3: 0.02Dy3+/0.01Sm3+ phosphors exhibited admirable thermal property with the activation energy 0.15 eV. Hence, the results strongly suggested that LiNbO3: Dy3+/Sm3+ phosphors could be applied to fabricate warm white LEDs.

Single-Phase Silicate Phosphors (Ba1.3Ca0.7−xSiO4:xDy3+) Doped with Dysprosium for White Solid-State Lighting

Single-phase phosphors have potential advantages such as simple processability, competitive cost, and other optical and optoelectronic properties. Hence, in this study, the silicate phosphors (Ba1.3Ca0.7−xSiO4:xDy3+) doped with Dy3+ ions (x = 0.01–0.05) were synthesized and characterized in detail. X-ray diffraction patterns showed that all the silicate phosphors have a τ-phase hexagonal unit cell independent of doping. However, d-spacing was reduced for the doped samples, indicating that the interplanar interactions were enhanced. Resultantly, the doped phosphors exhibited relatively larger domains with connectivity than the host, although there were sometimes microscale pores. Photoluminescence spectra stipulated that the optimized doping concentration is x = 0.03 for the silicate Ba1.3Ca0.7-xSiO4:xDy3+ phosphors. Finally, the CIE coordinates (0.30, 0.33) confirm that the Dy3+-doped silicate phosphors are well applicable to the white light-emitting diodes for solid-state lighting and display devices.

Regulation of Local Site Structures to Stabilize Mixed-Valence Eu2+/3+ under a Reducing Atmosphere for Multicolor Photoluminescence.

Co-doping mixed-valence Eu2+/3+ in a single-phase phosphor is an efficient method to realize the emission color regulation, which holds great potential for anticounterfeiting and ratiometric temperature sensing. Here, the mixed-valence Eu-doped Sr1.95+xLi1-xSi1-xAlxO4F (0 ≤ x ≤ 0.25) phosphors were designed and prepared under a reducing atmosphere. The correlation of local phase structures and luminescence properties was discussed. Replacing Si4+-Li+ ion pairs with Al3+-Sr2+ ion pairs compresses the Sr sites occupied by Eu2+, and it stabilizes Eu3+ in a reducing atmosphere and leads to the coexistence of Eu2+ and Eu3+ in single-phase Sr1.95+xLi1-xSi1-xAlxO4F:0.05Eu (0 ≤ x ≤ 0.25) phosphors. Based on the wavelength-dependent luminescence color behaviors of Sr1.95+xLi1-xSi1-xAlxO4F:0.05Eu phosphors, the fluorescent anticounterfeit papers/patterns containing Sr1.95+xLi1-xSi1-xAlxO4F:0.05Eu phosphors were the same as ordinary paper under ambient conditions. However, the hidden colors or images can be read out with green-orange luminescence under 365/300 nm light excitation. Benefiting from the diverse thermal response emission behaviors of Eu2+ (530 nm) and Eu3+ (703 nm), Sr1.95+xLi1-xSi1-xAlxO4F:0.05Eu phosphors exhibit temperature sensing performances, with the maximum absolute and relative sensitivity being 0.0294 K-1 at 573 K and 0.83% K-1 at 348 K. More importantly, Sr1.95+xLi1-xSi1-xAlxO4F:0.05Eu phosphors showed excellent stability in humid, acid, and alkali environments, which contributed to applying mixed-valence Eu2+/3+-doped Sr1.95+xLi1-xSi1-xAlxO4F to the fields of multicolor anticounterfeiting and noncontact optical thermometry.

Influence of anionic substitutions on the luminescent properties of Ca9.75Eu0.5(VO4)7

A series of substituted vanadates of Ca9.75±δEu0.5(XO4)0.1(VO4)6.9 (X ​= ​W6+, Nb5+, Ge4+, Cr6+, P5+) with Ca3(VO4)2-type structure have been synthesized via a standard solid-state method. Powder X-ray diffraction (PXRD), photoluminescence excitation (PLE) and emission (PL) spectra were used to characterize the solid solutions. The successful substitutions in the anionic part were confirmed using energy dispersive X-Ray (EDX), atomic emission spectrometry with inductively coupled plasma (ICP-OES) and the X-ray photoelectron spectroscopy (XPS) analyzes. All compounds crystallize in the noncentrosymmetric spаcе group R3c. The replacement of vanadium by other cations is accompanied by an increase in the second harmonic signal, with the exception of chromium. Red-to-orange (R/O) factors indicate a lower local symmetry of emitting Eu3+ ions environment in Ca9.75±δEu0.5(XO4)0.1(VO4)6.9 (X ​= ​W6+, Nb5+, Ge4+, Cr6+, P5+) in comparison to pure Ca9.75Eu0.5(VO4)7. Photoluminescence properties of Ca9.75±δEu0.5(XO4)0.1(VO4)6.9 systems were improved by NbO43− and GeO44− substitutions. The present study shows that Ge-incorporation in the β-Ca3(PO4)2 host increases the luminescence intensity in 2.5 times. The presented results indicate that the synthesized solid solutions can be considered as new single-phase phosphors.

Tunable White Light Emission and Energy Transfer in Liymgwo6: Dy3+, Tm3+ Single-Phase Phosphor

Tunable White Light Emission and Energy Transfer in Liymgwo6: Dy3+, Tm3+ Single-Phase Phosphor

Photoluminescence properties of Eu-doped WO3-Eu2(WO4)3 composites and single-phase Eu2(WO4)3 powders

The development of highly stable and efficient oxide-based red phosphors is urgently required for next-generation lighting devices. Herein, we report the micro/crystal structures and luminescent properties of single-phase Eu2(WO4)3 and Eu3+-doped WO3-Eu2(WO4)3 composite phosphors prepared by a one-step conventional solid-state reaction method in air atmosphere. As increasing Eu contents in the mixtures of WO3 and Eu2O3, the intensities of the X-ray diffraction peaks of Eu2(WO4)3 increased while that of WO3 decreased. The photoluminescence intensity of the synthesized phosphors increased with increase in the Eu content when calcined at 900 °C, while it degraded at a higher temperature. Red-emitting single-phase Eu2(WO4)3 powders were successfully obtained when the WO3 and Eu2O3 powders were calcined in the ratio of 3:1. The intensity of the red emission spectra of the Eu2(WO4)3 phosphor was higher than those of the 6, 12, and 24 at.% Eu-added WO3 composites at excitation wavelengths of 394 and 465 nm. On the other hand, the intensity of emission from the single-phase phosphor was lower than that of the Eu-doped WO3-Eu2(WO4)3 composites under excitation of UV light at 254 nm. Thus, we propose two prospective phosphors for application as red phosphors at various wavelengths.

Extension of Spectral Shift Controls from Equivalent Substitution to an Energy Migration Model Based on Eu2+/Tb3+-Activated Ba4-xSrxGd3-xLuxNa3(PO4)6F2 Phosphors.

Single-phase phosphors with tunable emission colors are crucial to develop high-performance white light-emitting diodes since they are valuable to improve the energy efficiency, color rendering index, and correlated color temperature. Most of the studies have been conducted to control the spectral shifts via a polyhedral distortion or chemical unit cosubstitution strategy. The combination of host optimization and dopant activator design in a single-phase phosphor system is very rare. Herein, a partial substitution strategy of [Ba2+-Gd3+] by [Sr2+-Lu3+] has been employed in Ba4-xSrxGd3-x-yLuxNa3(PO4)6F2/5% Eu2+ (x = 0-0.40) phosphors. Also, the energy migration from Eu2+ to Tb3+ ions has been investigated in as-prepared samples. Consequently, the emitted signal is observed to shift from 470 to 575 nm derived from equivalent substitutions, which is attributed to specific performance by the emission profile of Eu2+, and such results are closely related to splitting of the crystal field and energy transfer among various luminescent centers. Moreover, the tunable yellowish-green emitting material has been assembled by incorporating ion pairs (Eu2+ → Tb3+) into the Ba3.85Sr0.15Gd2.85Lu0.15Na3(PO4)6F2, and their relative ratios are varied. The corresponding Eu2+ → Tb3+ energy migration process is assigned to be the dipole-quadrupole interaction by the Inokuti-Hirayama model. This work provides rational guidance for the design and discovery of new products with tunable emission colors, originating from the cosubstitution strategy and energy conversion model.

Facile synthesis of BaMoO4 and BaMoO4/BaWO4 heterostructures with type -I band arrangement and enhanced photoluminescence properties

A series of BaMoO4 and BaMoO4/BaWO4 phosphors were successfully prepared via a polyacrylamide gel method and low temperature calcination technology. The effects of sintering temperature and mass percentage of BaMoO4/BaWO4 on the phase purity, functional group, surface morphology, charge state, photoluminescence properties and photocatalytic activity of the prepared products were studied in detail. The results indicate that the BaMoO4 phosphor is a scheelite tetragonal structure with high crystallinity. The photoluminescence spectra indicates that the phosphors have a strong blue emission peak at 440 nm with excitation wavelength of 282 nm for the BaMoO4 phosphor, and three emission peaks at 400, 440 and 460 nm with excitation wavelength of 284 nm for the BaMoO4/BaWO4 phosphors. These photoluminescence behaviors can be ascribed to the 1T2→1A1 transition, Jahn–Teller distorted tetrahedral symmetry of [MoO4]2- and surface defect. Photocatalytic experiments further confirmed that the BaMoO4/BaWO4 phosphors exhibit a high recombination rate of electron hole pairs. The result further indicates that the type-I band arrangement structure of BaMoO4/BaWO4 phosphors is beneficial to enhance the photoluminescent properties of single-phase phosphors. This study provides a novel route for preparing the type-I band arrangement structure composite phosphors with high photoluminescent properties and potential applications in light emitting devices, optoelectronic devices, laser devices and white pigments.

Controlling Cr3+/Cr4+ concentration in single-phase host toward tailored super-broad near-infrared luminescence for multifunctional applications

Full control on the valence of the active ions in solids to improve properties is the central topic of chemistry and materials. Cr3+ and Cr4+ ions generally emit wavelength-different near-infrared (NIR) light. Here, we have developed a chromium valence-controllable single-phase phosphor, Mg2GeO4:Cr3+,Cr4+ to achieve super-broad NIR luminescence. High Li + content charge compensators can stabilize Cr3+, whereas high-temperature sintering tends to facilitate the formation of Cr4+. Through fine adjusting the synthesis conditions, pure Cr3+ or Cr4+ luminescence can be obtained with peak emission locating at 935 nm and 1190 nm, respectively. Super broad band dual emission spanning from 650 nm to 1600 nm is realized via fully controlling the concentration ratio of Cr3+ to Cr4+ in a single host. By measuring the transmission spectra of several foodstuff illuminated by our phosphors, non-destructive analysis in food safety areas can be realized. This study provides a new strategy for exploiting super broad band NIR luminescent materials.

A fluorescence/phosphorescence dual-emitting metal-organic framework exhibiting two approaches for single-phase white-light emission

The unique features of metal–organic frameworks (MOFs) endow the huge advantages for room-temperature phosphorescence (RTP) and as host matrices for multiple emission and single-phase white light. Herein, a new biluminescent MOF ([Cd3(TCPBDA)2]·8DMF·2H2O, 1) was successfully synthesized. Compound 1 itself exhibits the white-light emission due to fluorescence-phosphorescence dual emission. To the best of our knowledge, it is the first example that the single-phase white emission could be obtained by the construction of biluminescent MOF. Compound 1 was also employed as the energy transfer host matrix with the encapsulation of red guest emitter 4-(dicyanomethylene)-2-methyl-6-(p-dimethylaminostyryl)-4H-pyran (DCM) into framework via one-pot process. The high energy transfer efficiency was occurred from host to guest, importantly, the single-phase phosphor DCM@1–1 (0.15 ​wt% DCM) displays warm white light with CIE coordinates of (0.33, 0.33). In addition, a WLED lamp with compound 1 as phosphor was prepared, exhibiting moderate correlated color temperature (CCT) of 4779 ​K and color-rendering index (CRI) of 71. These results open a new perspective for the development of single-phase white-light materials.

A new single-phase NaBi(WO4)2:Dy3+, Eu3+ phosphor with excellent thermal stability for NUV-excited warm white LEDs

A variety of Dy3+ single-doped and Dy3+, Eu3+ co-doped NaBi(WO4)2 phosphors were synthesized by the high temperature solid state method. The XRD patterns and Rietveld refinement measurement were operated to identify the crystalline phases. When the NaBi(WO4)2: 0.08Dy3+, yEu3+ phosphors were excited by 352 nm light, the energy transfer efficiency can be reach to 72.576% and the type of energy transfer mechanism was dominated by the dipole-dipole interaction. The thermal stability of specific NaBi(WO4)2: 0.08Dy3+, 0.1Eu3+ phosphor was tested and the PL emission intensity at 423 K drops to about 77.2% of that at 303 K, and the warm white light can be obtained after varying the Eu3+ ion concentration. Aforementioned results manifest that these as-prepared samples are expected to be the potential single-phase phosphors used in the areas of solid state lighting.