Red-emitting Phosphor Research Articles

Preparation and Luminescence Property Study of Red-Emitting Na3.6Y1.8(PO4)3:Eu3+,Li+/K+ Phosphors with Excellent Thermal Stability for Light-Conversion Application

A series of red-emitting phosphors, Na3.6Y1.8−x(PO4)3:xEu3+, have been synthesized by a high-temperature solid-phase method. The impact of the partial Li+/K+ ion substitution on the crystal structure and photoluminescence (PL) performance of Na3.6Y1.05(PO4)3:0.75Eu3+ phosphor have been investigated. Various techniques have been used for characterization of the as-obtained materials. X-ray diffraction (XRD) analysis was utilized to confirm the composites of these samples, and the morphology and element distribution were examined by scanning electron microscope (SEM) and transmission electron microscope (TEM). This study found that the developed Na3.6Y1.8−x(PO4)3:xEu3+ phosphors exhibited a prominent emission peak at ~620 nm when excited at 393 nm, which corresponded to 5D0 → 7F2 transitions of Eu3+ ions. Furthermore, the robust emission peak at ~705 nm (5D0 → 7F4) of these phosphors enables a better match with plant pigment absorption. Beyond that, the partial substitution of Li+/K+ ions probably changed the crystal structure, and reduces the symmetry around Eu3+, leading to significantly enhanced luminous intensities by 23.24% and 18.29%, with the highest quantum yields (QYs) reaching 99.85% and 96.29%, respectively. Additionally, the prepared phosphors show non-thermal quenching and superior thermal stability at elevated temperatures from 298 to 473 K. These findings and results suggest that Li⁺/K⁺-substituted Na3.6Y1.05(PO₄)₃:0.75Eu3⁺ phosphors can serve as promising red-emitting phosphors for plant lighting applications.

Photoluminescence properties of Mn2+-activated red-emitting phosphors with superior thermal stability for backlighting display applications

The red-emitting phosphors, Na2Mg1-x(PO3)4:xMn2+ with concentrations ranging from 0.01 to 0.11, have been successfully synthesized using a simple solid-state method. The as-synthesized phosphors are crystallized in an orthorhombic structure. The luminescence mechanism of Mn2+ ions in Na2Mg(PO3)4 lattice has been deeply explained using the Tanabe-Sugano (T-S) energy level diagram for the d5 electron configuration. The typical photoluminescent emission (PL) and photoluminescent excitation (PLE) spectra were measured. Several excitation peaks in the spectral range of 250–550 nm on the PLE spectrum and a strong emission peak at 613 nm indicate that the as-synthesized phosphors can be effectively excited using ultraviolet (UV) and near-UV LED chips. Several photometric characteristics were measured, such as the Commission International de'LEclarirage (CIE) chromaticity coordinate (x, y), color purity (CP), and correlated color temperature (CCT), corresponding to the concentration-dependent PL spectra. Furthermore, the thermal stability of the Na2Mg1-x(PO3)4:xMn2+ phosphors was investigated through temperature-dependent PL spectra and decay curves from 10 to 500 K. All results confirm that the as-synthesized red-emitting phosphors exhibit excellent thermal stability, which are attractive characteristics for white light emitting diodes (W-LEDs) applications.

Synthesis, Structure and Luminescence Properties of Mn-doped MgAl2O4 Red-Emitting Phosphors with Varying Sintering Temperature.

Oxide matrix red-emitting phosphors are deemed as excellent color converters for white light emitting diodes (WLEDs) and laser diodes (LDs). Manganese-doped MgAl2O4 powder was synthesized by a solid-state reaction method at different sintering temperatures. Microstructure shows that grain size is mainly in the range of 0.2-5μm, and grain agglomeration occurs with increased sintering temperature. XPS analysis indicates that the doped Mn ion exhibits a valence state of + 4 within the MgAl2O4 matrix. The diffraction peak of the phosphors is shifted by the sintering temperature, which affects lattice constant. Upon excitation by 300nm ultraviolet light, the samples emit asymmetric broadband red light within the range of 620-720nm, attributed to Mn4+ ion's transition from 2Eg to 4A2g states. With the increasing temperature, the main emission peak shifts from 677nm to 650nm, ascribed to the change in energy level (2Eg) resulting from the reduction of Al2O3 phase. Crystal field theory confirmed that Mn4+ ions are within a strong crystal field environment created by MgAl2O4 matrix. By affecting particle size and crystallinity, the sintering temperature influences the fluorescence lifetime of the Mn4+ ion. Notably, these red-emitting phosphors exhibits remarkable thermal stability as their emission intensity remains approximately at 58% of initial intensity even at elevated temperature (435K). Consequently, Mn4+: MgAl2O4 red-emitting phosphors with high thermal stability render them promising candidates for WLED applications.

A red-emitting phosphor Na3AlF6:Mn4+: Green synthesis, optical characteristics, thermal stability and application in high-performance warm WLED

Mn4+-doped fluoride red phosphors have been widely used in warm WLEDs, but the preparation of such phosphor requires the use of a large amount of HF as a fluorine source and an acidic environment. How to reduce the excessive use of highly toxic HF in the preparation process and achieve green synthesis has become a hot research topic. Therefore, a simple green synthesis strategy is proposed in this work to synthesize a series of red-emitting phosphors Na3AlF6:Mn4+. The highly toxic HF solution is replaced by using a low toxicity reaction system (HCl/HNO3 + NH4F), which reduces the direct use of HF. X-ray powder diffraction, energy-dispersive X-ray spectrometer and scanning electron microscope are employed to determine the crystal structure, composition and morphology of all samples. Optical properties are characterized using excitation spectra, emission spectra and fluorescence lifetime curves. The calculation results indicate that the red-light has low correlated color temperature and the excellent color purity, and Na3AlF6 host can provide a strong crystal field environment for Mn4+. In addition, different aluminum sources and Mn4+ doping concentrations are used to explore the optimal preparation condition. The mechanisms of concentration quenching and thermal quenching have also been systematically explored. The stabilities of red-light emission intensity and color are investigated under the high temperature. The integral PL intensity at 423 K is 47 % of the initial value at 298 K. The activation energy, the chromaticity shift and the chromaticity coordinate variation are also systematically calculated. More importantly, a high-performance warm WLED with low correlated color temperature (CCT = 3296 K) and high color rendering index (Ra = 94.7) is achieved by using Na3AlF6:Mn4+ as a red-emitting material. Not only that, the warm WLED exhibits strong output stability under high driving current. The discovery of this work provides a comprehensive understanding for the rational design of high-performance Mn4+-activated fluoride red phosphors via a simple green synthesis strategy.

Development of Mg2TiO4:Mn4+ phosphors for enhanced red LED emission and forensic fingerprint analysis

The advancement in the development of inorganic phosphors marks a significant milestone in the fields of LED technology and forensic science. Herein, Mg2TiO4:Mn4+ (MTO:Mn4+) novel red-emitting phosphors are synthesized through a solvothermal method, which demonstrates a promising approach for enhancing latent fingerprint detection capabilities and improving the performance of red LEDs. The confirmation of the cubic structure post-annealing and the nano-nature as revealed by TEM analysis underpin the MTO:Mn4+ phosphors suitability for these applications. The broad excitation spectra and the sharp red emission at 659 nm, coupled with the optimal doping concentration, showcase the MTO:Mn4+ phosphor's efficient luminescence properties. Moreover, the calculated critical distance between Mn4+ ions (32.906 Å) elucidates the concentration quenching mechanism, which is pivotal for optimizing the performance. The high purity of the emitted red light (97.2 %) and the precise CIE coordinates (0.5969, 0.2926) of the MTO:Mn4+ phosphor suggest its potential for producing high-quality red LEDs. Additionally, the capability of MTO:Mn4+ phosphors to reveal detailed and high-resolution latent fingerprints offers a more reliable and efficient method for processing and analyzing crucial evidence. These findings not only contribute to the scientific understanding of MTO:Mn4+ phosphor materials but also pave the way for their practical application in cutting-edge technologies.

Garnet-structure phosphors with ultra-high color purity red emission for potential warm WLED and flexible-transparent displays

Red-emitting phosphors play a pivotal role in the field of lighting technologies. This study introduces an innovative class of Li6SrEu2Sb2O12 garnet-structured phosphors, distinguished by the resistance to concentration quenching. A comprehensive examination of the crystal structure, electronic configuration, and photoluminescence characteristics has been conducted. Notably, the doping Eu3+ ions and their doping concentrations barely affected the crystal structure and morphology, and the band gap slightly decreased as the doping concentration increased. Interestingly, the obtained samples exhibit an ultra-high color purity, good thermal stability (78.60 % at 423 K), and suitable internal photoluminescence quantum yield (44.18 %). Consequently, a phosphor-converted white LED has been successfully fabricated, which boasts an outstanding correlated color temperature of 3271 K. Beyond conventional application, this research also introduces the concept of innovative flexible-transparent displays harnessing the phosphor film. Overall, this work has synthesized a groundbreaking red-emitting phosphor, poised to enhance traditional lighting sources and potentially pave the way for new applications in the field of advanced optical displays.

Enhanced luminescence performance in double perovskite CaSrLaSbO6: Mn4+ red emission phosphors for indoor plant growth via cation doping

Novel CaSrLaSbO6: Mn4+ red-emitting phosphors with double perovskite structure were successfully synthesized by the high-temperature solid-phase method. CaSrLaSbO6:Mn4+ phosphor showed a broad excitation band with different excitation peaks from 250 nm to 600 nm owing to the Mn4+-O2- charge transfer and 4A2g → (4T1g, 2T2g, and 4T2g) transitions of Mn4+ ions and exhibited intense deep-red emission at 678 nm attributed to the 2Eg → 4A2g transition of Mn4+ ions. To further enhance the performance of the phosphor, a cation doping method was adopted in this paper to synthesize CaSrLa1-xLnxSbO6: Mn4+ (Ln = Gd, Y) phosphors. The luminescence intensity of the samples was enhanced after doping with different cations, and the related mechanism was discussed. In addition, the microstructure and crystal field environment were systematically investigated. The luminescence intensity of the CaSrLa0.85Y0.15SbO6: Mn4+ phosphor was about 1.82 times higher than that of CaSrLaSbO6: Mn4+phosphor. The emission spectrum of the sample matched well with the absorption band of plant pigments. Furthermore, the plant growth LEDs and light-conversion film were prepared by using the optimized CaSrLa0.85Y0.15SbO6: Mn4+. The results indicate that the designed phosphors have great potential applications in agricultural cultivation.

An efficient red phosphor LuNb2VO9:Eu3+ with broadband excitation and abnormal thermal quenching properties for personal identification, security ink, and w-LEDs

A series of red-emitting phosphors LuNb2VO9 (LNV):xEu3+ (x = 0.5–45 mol%) were successfully obtained through the high-temperature solid-state reaction. The structure, phase purity, photoluminescence spectra, thermal stability properties, and color purity of the obtained phosphors were systematically examined. The LNV:Eu3+ phosphor exhibits broadband excitation due to the O2-→Eu3+ and O2-→V5+ charge transfer. The LNV:Eu3+ phosphor excited at 316 nm shows four emission peaks at 595, 615, 619, and 699 nm, corresponding to electron transitions from the 5D0 level to the 7F1, 7F2, 7F3 and 7F4 levels. The optimal doped concentration of LNV:xEu3+ is x = 10 mol%. The quenching mechanism is attributed to the nearest neighbor ion interaction. Furthermore, the prepared phosphor exhibits good thermal stability and remarkable activation energy Ea (0.74 eV). In addition, LNV:Eu3+@oleic acid (OA) readily exhibits the level I-III characteristics of fingerprints and the detailed characteristics of lip lines. The successful utilization of LNV:Eu3+ in anti-counterfeiting ink has yielded impressive results. The Commission International de L′ Eclairage (CIE) coordinate of the prepared white light-emitting diode (w-LED) in this study is (0.331, 0.367), accompanied by a color rendering index (Ra) of up to 95. Notably, the results of these experiments indicate that LNV:Eu3+ phosphor possesses exceptional luminescence properties and holds promising applications.

Influence of Mg doping on structure and optical properties of red-emitting phosphor Li2TiO3:Mn4+

Li2TiO3:Mn4+ has been previously identified as a potential candidate to replace commercial red-emitting Eu2+-activated phosphors. Its luminescent efficiency is limited by the presence of defects and the sensitivity of Mn4+ to redox processes. A series of co-doped Li2TiO3: x Mg2+, 0.01 Mn4+ samples were prepared to gain insight on the effect of electron doping on the structure and photoluminescent properties, through characterization by powder X-ray diffraction, elemental analysis, and optical spectroscopy. As Mg2+ substitutes for Li+, the ordered arrangement of cations within the honeycomb layers in the parent structure (Li2SnO3-type, an ordered derivative of rocksalt) gradually transforms to a more disordered arrangement. The increased cation site disorder leads to less intense and broader emission peaks as well as lower quantum yields.

Isomorphism of Sr[Li3AlO4] and Sr[Li3GaO4] - Syntheses, Crystal Structure, and Europium(II) Luminescence.

While highly efficient red-emitting inorganic phosphors have been discovered in the substance class of alkaline earth oxo(nitrido)lithoaluminates, new narrow-band green- and yellow-emitting components are being sought to improve the performance of phosphor-converted light-emitting diodes (pc-LEDs). Various solid-state reactions were carried out under protective gas atmosphere in nickel crucibles and sealed tantalum ampules to synthesize Sr[Li3AlO4], Sr[Li3GaO4], and five substitutional derivates of Sr[Li3(Al1-x Ga x )O4] at moderate temperatures. The observation of a linear increase in the unit cell parameters as a function of the increasing gallium mole fraction x in Sr[Li3(Al1-x Ga x )O4] revealed Vegard behavior in the solid-solution series, which was derived from powder X-ray diffraction data. The isomorphic crystallization of the new oxolithogallate Sr[Li3GaO4] and the known oxolithoaluminate Sr[Li3AlO4] in an ordered variant of the U[Cr4C4] aristotype was verified on the basis of powder and single-crystal X-ray diffraction data. Photoluminescence spectroscopy was used to investigate the narrow-band emissions in the substitution series of Eu2+-activated Sr[Li3(Al1-x Ga x )O4] under blue-light excitation. The emission maximum was shifted to higher energies as the gallium mole fraction increased. Peak wavelengths were observed at λem = 572 nm (fwhm equals 47 nm, 1446 cm-1, 0.18 eV) for yellow-emitting Sr[Li3AlO4]:Eu2+ and at λem = 554 nm (fwhm equals 49 nm, 1589 cm-1, 0.20 eV) for green-emitting Sr[Li3GaO4]:Eu2+. Sr[Li3AlO4]:Eu2+ has excellent thermal quenching resistance with a photoluminescence emission intensity of >93% at T = 423 K relative to the room temperature value, making this inorganic phosphor a potential candidate for solid-state lighting applications.

Unveiling the Versatility of Coumarin-Integrated with Phenanthroline/Thiabendazole-Based EuIII Complexes for Smart LEDs, Vapoluminescence, and Bioimaging Applications.

Narrow band red-emitting phosphors based on organo-Eu(III) complexes prove their energetic features with surprising performance in smart red/white LEDs, sensing, and biological fields. In this report, a series of unique Eu(III) complexes have been synthesized with coumarin integrated with a class of phenanthroline(Phen)/thiabendazole(TBZ) based ancillary ligands and dibenzoyl methane (DBM)/2-theonyl trifluoroacetone (TTA) as an anionic ligand. The computational study reveals that the TBZ/Phen-based neutral ligands are superior energy harvesters to those other reported analogue neutral ligands. All the Eu-complexes demonstrated outstanding red emission due to electric dipole (ED) transition (5D0 → 7F2) in solid, solution, and thin film with high quantum yield (QY). Theoretical analysis (TD-DFT) and experimental findings describe that the energy transfer (ET) from the ligand's triplet level to the Eu(III) ion is completely occurring. The Eu(III) complexes can potentially be used to fabricate intense hybrid white and red LEDs. All of the fabricated red LEDs revealed high luminous efficiency of radiation (LER) values. The fabricated blue LED based hybrid white LEDs displayed remarkable performance with a low correlated color temperature (5634 K), high color rendering index 88%, and CIE values (x = 0.33; y = 0.342) for 3Eu. By interaction with acid-base vapors, Eu-complexes displayed effectively alterable on-off-on luminescence. Further, cellular imaging shows that Eu-complexes can be a potential biomarker for cancer cell lines.

Synthesis and photoluminescence of Ba1-xSrxMgSi4O10:Eu2+ phosphors for warm white light-emitting-diodes

Efficient and thermally stable blue-cyan-emitting phosphors are urgently demanded to cover the “cyan gap” for high quality light-emitting-diodes (LEDs) lighting. This work provides a series of blue to cyan color-tunable Ba0.96-xSrxMgSi4O10:0.04Eu2+ phosphors developed via solid-solution method. The phase transformation, photoluminescence, quantum efficiency and thermal stability were investigated in detail. Notably, Sr2+ substitution is effective to red-shift the emission toward cyan emission (from 465 to 480 nm). Simultaneously, the quantum efficiency and thermal stability can be well maintained. Finally, using a 365 nm near-ultraviolet (NUV) LED chip combining with the as-prepared blue-cyan-emitting phosphor, β-SiAlON:Eu2+ green-emitting phosphor and CaAlSiN3:Eu2+ red-emitting phosphor, a warm-white LED device was fabricated with correlated color temperature (CCT) of 4329 K, and color-rendering index (CRI) of 92. These results indicate that the Ba1-xSrxMgSi4O10:Eu2+ blue-cyan-emitting phosphors may have potential applications for high quality NUV-pumped warm-white LED lighting.

Dazzling red-emitting Ca2EuMO6 (M = Sb, Nb, Ta) double-perovskite phosphors with potential application in phosphor-converted white light-emitting diodes

In this paper, three new efficient Eu3+-activated Ca2EuMO6 (M = Sb, Nb, and Ta) red-emitting phosphors with outstanding luminescence properties were prepared by using the high-temperature solid-state reaction method. X-ray diffraction and Rietveld refinements revealed the double-perovskite structure of Ca2EuMO6 (M = Sb, Nb, and Ta) compounds. Photoluminescent excitation and emission spectra, decay lifetimes, CIE chromaticity coordinates, color purity values, internal quantum efficiency, and thermal stability were discussed in detail. Under the excitation of 395 nm near-ultraviolet light, these Ca2EuMO6 (M = Sb, Nb, and Ta) phosphors demonstrated bright narrow-band red emissions with peaks at 592, 620, 656, and 703 nm due to the 5D0→7FJ (J = 1–4) transitions of Eu3+ ions. The internal quantum efficiencies of the Ca2EuSbO6, Ca2EuNbO6, and Ca2EuTaO6 samples were determined to be 39.3%, 41.6%, and 40.4%, respectively. Impressively, the emission intensity of Ca2EuNbO6 is about 1.25 times higher than that of commercial Y2O3:Eu3+ red phosphor. CIE color coordinates of Ca2EuMO6 (M = Sb, Nb, and Ta) phosphors were calculated to be (0.6748, 0.3250), (0.6800, 0.3198), and (0.6790, 0.3208), respectively; along with high color purity of 90.7%, 93.2%, and 92.7%. Besides, their thermal stability was also investigated, and the corresponding emission intensities of Ca2EuMO6 (M = Sb, Nb, and Ta) at 423 K were respectively maintained at 73%, 86%, and 80% of that at 303 K. All results show that these newly developed red-emitting Ca2EuMO6 (M = Sb, Nb, and Ta) phosphors possess potential applications in white light-emitting diodes.

A novel Mn4+-doped Li2Mg4TiO7 red-emitting phosphor for warm white light-emitting diodes

To improve the light quality of warm white-LEDs (w-LEDs), novel Mn4+-activated red-emitting phosphors that can be excited efficiently by blue light with yield high performance are highly imperative. Here, we report a Mn4+-doped Li2Mg4TiO7 (LMT) phosphor prepared via a traditional high-temperature reaction method. The crystal structure and luminescent properties of the LMT:Mn4+ phosphors are studied. An excitation band centered at 470 nm, matches well with the commercial blue LED chips. Upon blue light excitation, a broadband red emssion located at 673 nm due to d-d transitions of Mn4+ is observed. The optimum doping concentration of Mn4+ is determined to be x = 0.08 %. The optimized red-emitting phosphor LMT:Mn4+ attains a photoluminescence quantum yield (PLQY) of 40.0 % and a good thermal resistance (ΔE = 0.43 eV). The combination of the as-obtained red-emitting phosphor, commercially available yellow phosphor, and blue LED chip yields a warm w-LED device, delivering CIE (x, y) = (0.3922, 0.3909), CRI = 70.0 and CCT = 2214 K. Therefore, this work provides a novel LMT:Mn4+ phosphor as a potential red component for warm w-LEDs.

Amplification of intense red emission through integrating Li+ ions to V2O5:Eu3+ phosphors: Optical thermometry, cheiloscopy and extraction of level III features for individual identification

This study presents the synthesis of V2O5:Eu3+ phosphors in concentrations ranging from 1 to 9 mol %, using a solution combustion method with Areca Nut (A.N) as a bio-fuel. The samples exhibit an orthorhombic crystal structure, confirmed by powder X-ray diffraction (PXRD), and rod-like morphology as shown by field emission scanning electron microscopy (FE-SEM). Photoluminescence (PL) studies reveal that the emission intensity of the 5D0→7F2 transition at 619 nm increases with the Eu3+ concentration up to 5 mol %, where it peaks before quenching due to quadruple-quadruple interactions, according to the Van Uitert relation. To improve luminescence, Li+ ions are added, with the V2O5:5Eu3+ co-doped with 4Li+ (V2O5:5Eu3+, 4Li+) ions showing the highest PL intensity, about 5.03 times higher than that of Eu3+ alone. This optimized phosphor has Commission Internationale de l’Eclairage (CIE) chromaticity coordinates of (0.6022, 0.3963), closely matching commercial red-emitting phosphors and demonstrating a colour purity (CP) of 88.69 %. Thermal stability assessments indicate that these phosphors have a high activation energy (Ea) of about 0.224 eV, signifying robust thermal properties. The optimized V2O5:5Eu3+, 4Li+ phosphors efficiently reveal level I–III features in latent fingerprints (LFPs) and accurately identify lip prints (LPs) groove patterns of type I–VI under 365 nm UV light, providing high resolution and contrast. These characteristics make the optimized phosphor an excellent candidate for use in photonic devices, advanced forensic and data security applications.

Regulating the luminescence properties of Eu2W3O12 red-emitting phosphor via rare-earth ions doping for optical thermometry, white light-emitting diode and plant growth applications

To fulfil various applications, series of rare-earth (RE) ions (i.e., La3+, Gd3+, Sm3+) doped Eu2W3O12 (EWO) phosphors were synthesized. All the designed phosphors can emit glaring visible lights from Eu3+ and their fluorescence intensities were significantly enhanced through RE ions doping. To explore the impact of RE ions doping on the symmetric properties of Eu3+ in studied samples, theoretical calculation based on Judd-Ofelt theory was performed. Moreover, through utilizing temperature-related emission spectra, the thermal quenching behaviors of resultant phosphors were studied and found that their thermal stability had been improved by adding RE ions. Furthermore, the thermometric properties of designed phosphors were examined through adopting the single-band ratiometric technique to analyzing the temperature-dependent fluorescence intensity ratio of the emission band arising from 5D0 → 7F2 transition of Eu3+. It is found that maximum absolute and relative sensitivities of resulting phosphors were 0.197 and 1.202 % K−1, respectively. Additionally, two types of devices, i.e., white light-emitting diode (white-LED) and red-emitting LED, where the prepared phosphors play as red-emitting components, were fabricated. The packaged white-LEDs can emit warm white light with high color rendering index and low correlated color temperature, which are insensitive to operating current. Considering the red-emitting LEDs, their emission bands overlap with the absorption bands of plant pigments, which can promote plant growth and it was verified by peppermint growth experiments. These results verify that the introduction of RE ions is a feasible approach to modify the luminescence performances of phosphors to realize diversified applications.

Spectroscopic investigation of novel Eu3+ doped Na2LiAlF6 fluoroaluminate for solid state lighting applications

Red-emitting phosphors are crucial for sustainable white-light-emitting diodes (WLEDs) used in lighting. These materials significantly enhance the lighting and backlit display quality of phosphor-converted white LEDs (pc-WLEDs) by overcoming red deficiency. Luminescent properties of rare earth activated fluoride based inorganic compounds are most investigated due to its excellent spectral characteristics. In this paper we report the novel Na2LiAlF6 luminescent host material activated with Eu3+ rare earth ions synthesized by wet chemical method. The spectral analysis revels the excitation spanning in near UV region while emission spectra depict characteristic peaks transitioned in accordance with 5D0 to 7F1 and 7F2. Effect of concentration quenching, Color purity and temperature studied briefly which demonstrates that the prepared red emitting phosphor is useful in various device applications such as phosphor converted White light emitting diodes for fulfilment of red deficiency, solid state lighting, display technology as an essential red component.

A Lu3Sc2Ga3O12: Eu3+ red-emitting phosphor with excellent optical properties and thermal stability was obtained by partially replacing Lu3+ with Gd3+ / Y3+

A novel red phosphor Lu3(1-x)Sc2Ga3O12: xEu3+(0 ≤ x ≤ 0.3) was successfully prepared by high temperature solid state method. The Lu2.4Sc2Ga3O12: 0.2Eu3+ phosphor shows strong high internal quantum efficiency and thermal stability with values of 64.79 % and 87.0 %, respectively. Based on Lu2.4Sc2Ga3O12: 0.2Eu3+ phosphor, the partial replacement of Lu3+ ions in the host by Gd3+ / Y3+ ions changes the local crystal field environment of Eu3+ ions, resulting in wonderful changes in the luminous center, and the luminous intensity at 593 nm is increased by 3.66 and 3.54 times, respectively. The decay time of Eu3+ ions is analyzed from the perspective of dynamics, and the reasons for the enhancement of luminescence after partial replacement of Lu3+ ions are discussed in detail from two aspects of phosphor structure and crystal field effect around Eu3+ ions. In addition, with the substitution of Gd3+ / Y3+ ions, the thermal stability of the sample is 90.3 %/89.4 % with excellent low thermal quenching. The thermal quenching mechanism is described by combining Debye temperature and activation energy. The sample also has a high internal quantum efficiency IQE=79.03 % / 78.24 %. Finally, under the excitation of 365 nm chip, the phosphors of Lu2.34Sc2Ga3O12: 0.2Eu3+, 0.02Gd3+ and Lu2.34Sc2Ga3O12: 0.2Eu3+, 0.02Y3+ synthesized R-LED device has extremely high color rendering index, Ra is 78.23/77.15 and color temperature is 1640.38 K/1642.97 K. The experimental results show that the Lu2.34Sc2Ga3O12: 0.2Eu3+, 0.02Gd3+ / Y3+ phosphors prepared has a wide application prospect in w-LED devices.

Synthesis and optical properties of highly efficient Na7Mg13La(PO4)12:Eu3+ powders with excellent thermal stability

In the pursuit of efficient red-emitting phosphors, a series of red-emitting Na7Mg13La(PO4)12:Eu3+ phosphors was prepared using a high-temperature solid-state synthesis method. The phase purity was monitored using powder X-ray diffraction (XRD). The morphological features of the synthesized samples were evaluated by taking scanning electron microscopy (SEM) images. The optical properties of the synthesized polycrystalline samples were investigated by recording room-temperature and temperature-dependent (77–500 K interval) excitation and emission spectra, and photoluminescence (PL) decay curves. The calculated TQ1/2 values were above 420 K, regardless of the Eu3+ concentration, indicating the high thermal stability of the phosphors. The optimal Eu3+ concentration was 100 %, which indicated the absence of concentration quenching in the given host. Furthermore, the quantum efficiency of fully Eu3+-substituted compound reached 100 %, which is an excellent feature for practical phosphor applications.

Ion exchange-assisted surface passivation toward highly stable red-emitting fluoride phosphors for light-emitting diodes

A facile and environmentally friendly ion exchange-assisted surface passivation (IASP) strategy is presented for synthesizing red emitting Mn4+-activated fluoride phosphors. A substantial, pristine Mn4+-free shell layer, applied as a coating to Mn4+ doped potassium fluorosilicate K2SiF6:Mn4+ (KSFM) phosphors, enhances both water resistance and luminescence efficiency. The stability test of fluoride in water at ambient temperature and boiling water demonstrates that IASP-treated KSFM phosphors are highly water resistant. Furthermore, both the negative thermal temperature (NTQ) fitting results and the photoluminescence (PL) decay confirm that the IASP process effectively passivates surface defects, leading to enhanced luminescence performance. The maximum internal quantum yield (QYi) of the IASP-KSFM phosphor is 94.24%. A white LED realized a high color rendering index (CRI) of 93.09 and luminous efficiency (LE) of 149.48 lm/W. This work presented a novel technique for the development of stable fluoride phosphors and has the potential to increase the use of KSFM phosphors in plant supplementary lighting systems and white light-emitting diodes.