Synthesis and optical characterization of novel Sr3Ga2O6:Eu phosphor

Alkaline earth metal gallets have been identified as an important ceramic material. The crystal chemistry of many of these gallets is well explored; however, very rare studies regarding optical properties of rare earth (RE) ions doped in such gallets, particularly in Sr₃Ga₂O₆ host, have been carried out. The present study reports on synthesis and characterization of novel Sr₃Ga₂O₆:Eu³⁺ phosphors. The phosphors have been synthesized using a conventional solid state reaction method. Crystal structure, morphology and luminescence properties (excitation, emission and CIE coordinate) of these phosphors have been studied as a function of sintering temperature and Eu³⁺ concentration. X-ray diffraction study reveals that the phosphor sintered at low temperature (900 °C) contains an impurity phase which is removed at higher sintering temperatures and results into cubic crystalline phase of Sr₃Ga₂O₆. Particle size of the phosphor increases with an increase in sintering temperature which results to a red shift in the peak position of excitation band lying in a broad range from 250 to 370 nm. Optimum emission intensity is attained for 0.12 mol% concentration of Eu³⁺ ions; above this concentration, a quenching in emission intensity is observed.     

Ca2+/Sr2+/Ba2+ dependent phase separation,nanocrystallization and photoluminescence in fluoroaluminosilicate glass

Fluoride phase separation is the initial stage of nanocrystallization in oxyfluoride glasses, and it is a key step in achieving transparent glass-ceramics with good luminescence. In this work, we combine molecular dynamics (MD) simulations and experimental studies to investigate the phase separation, nanocrystallization and photoluminescence in fluoroaluminosilicate glass and glass-ceramics containing alkali earth fluoride (MF₂). The results reveal different phase separation behaviors due to the field strength difference of M²⁺. The composition and size similarity between the fluoride-rich regions in the MD simulated glass and the fluoride nanocrystals in the experimental prepared glass-ceramics are observed, suggesting that the separated fluoride phase is the structural origin of the observed MF₂ nanocrystals. Besides, in order to understand the M²⁺ dependent glass structural features, the crystallization temperatures, the luminescent properties of Eu³⁺ and Eu²⁺ doped glass-ceramics, and the lasing performance of Er³⁺ doped glass-ceramics are discussed. Based on these comprehensions, some strategies are proposed to help to efficiently design oxyfluoride glass with desired luminescence performance.     

Synthesis and photoluminescence properties of Eu2+/Eu3+ or Ce3+/Eu3+ co-doped Sr5(BO3)3F compounds

The synthesis and photo-luminescence properties of Eu²⁺/Eu³⁺ or Ce³⁺/Eu³⁺ co-doped Sr₅(BO₃)₃F compounds are reported. Using the Sr₅(BO₃)₃F as the host, through the solid state reaction under the reductive atmosphere, Eu²⁺/Eu³⁺ and Ce³⁺/Eu³⁺co-doped samples were prepared. These compounds exhibit good photo-luminescence properties. Under the excitation of 376 nm, an unusual red orange emission coming from the Eu²⁺ ions can be obtained in Eu ions doped Sr₅(BO₃)₃F, which exhibits a broadband emission in the range of 450–800 nm with the peak at around 600 nm. At the same time, the characteristic f-f excitation and emission of Eu³⁺ can improve and adjust the Eu²⁺ emission in Eu³⁺/Eu²⁺ codoped Sr₅(BO₃)₃F. In addition, the adjustable luminescence properties from blue to white of Sr₅(BO₃)₃F:Ce³⁺, Eu³⁺ are investigated. The energy transfer behavior from Ce³⁺ to Eu³⁺ was confirmed. In the spectra of the co-doped samples, we can hardly observe the characteristic peak of Eu²⁺, because Ce⁴⁺ can oxidize Eu²⁺ to Eu³⁺, and Ce⁴⁺ itself is reduced to Ce³⁺. The CIE coordinates from (0.2758, 0.2420) to (0.3857, 0.3015) show Sr₅(BO₃)₃F:3%Ce³⁺, x%Eu³⁺ (x = 1,3,5,7,9) are in the white light emission region. All results demonstrate that the Sr₅(BO₃)₃F:Eu³⁺/Eu²⁺ and Sr₅(BO₃)₃F:Ce³⁺/Eu³⁺ phosphors have good application prospects for LED plant growth and white LED, respectively. The bond energy method was used to explain the reason why the Eu²⁺/Eu³⁺ ion instead of only Eu²⁺ and Ce³⁺/Eu³⁺ instead of Ce³⁺/Eu³⁺/Eu²⁺ can exist in the host Sr₅(BO₃)₃F. The theoretical analysis agree well with the experimental result.     

Photoluminescence and temperature sensing of lanthanide Eu3+ and transition metal Mn4+ dual-doped antimoniate phosphor through site-beneficial occupation

For a long time, rare-earth ion-doped phosphors have been widely used in temperature sensing because of their excellent light-emitting properties. However, most of the rare earth elements are relatively rare and expensive, so the transition group elements that are economical and easy to obtain have been favored by researchers. This paper presents a new type of phosphor doped with rare earth ion and transition metal for optical temperature measurement. In recent years, Mn⁴⁺-doped phosphors have attracted wide attention because of their strong deep red light-emitting properties. La₂LiSbO₆ provides a good host environment for Mn⁴⁺ and Eu³⁺ due to its unique crystal structure. In this paper, a series of La₂LiSbO₆ phosphors singly doped with Mn⁴⁺ and Eu³⁺, and co-doped with Eu³⁺/Mn⁴⁺ were synthesized. The crystal phases and optical properties of these materials were characterized and analyzed in detail. We specifically studied the temperature dependence of the fluorescence intensity of the optimized La₂LiSbO₆: Eu³⁺, Mn⁴⁺ phosphors at 303K–523K. The experimental results prove that the thermal responses of Mn⁴⁺ and Eu³⁺ are different. With increasing temperature, the thermal quenching of the Mn⁴⁺ fluorescence intensity is much faster than that of Eu³⁺, so the temperature characteristics can be explored by the fluorescence intensity ratio (FIR) of Eu³⁺ to Mn⁴⁺. At 523 K, its maximum relative sensitivity and maximum absolute sensitivity can reach 0.891% K⁻¹ and 0.000264 K^-1, respectively. Our experimental analysis shows that La₂LiSbO₆:Eu³⁺/Mn⁴⁺ phosphors have relatively high temperature sensitivity and have potential application prospects in the field of high temperature sensing.     

New single‐component multicolor emission Na1−xAl1+2xSi1−2xO4:xBi3+/Eu3+ phosphors via energy transfer

A series of emission‐tunable Na_1?xAl_1+2xSi_1?2xO₄:xBi³⁺/Eu³⁺ phosphors were synthesized via high temperature solid‐state reaction method. The luminescence properties, energy transfer from Bi³⁺ to Eu³⁺ ions, color tuning, thermal stability and quantum efficiency were systematically investigated. Especially, in the host, a certain amount of Si⁴⁺ were replaced by Al³⁺ in order to remedy the charge compensating defect, so that, the emission intensity had been improved. The results of Rietveld refinements, the analysis of SEM mapping and the fourier transform infrared (FT‐IR) indicated that this charge balance strategy was an effective method. Meanwhile, the energy transfer from Bi³⁺ to Eu³⁺ can be inferred and confirmed and the mechanisms were demonstrated to quadrupole–quadrupole interaction. The emission hue can be tuned from blue to pink, and finally to orange red light by properly varying the ratio of Bi³⁺ and Eu³⁺. Importantly, when the temperature was raised to 150°C, the integrated emission intensity was 71.20% of the initial value for NAS:1%Bi³⁺,2%Eu³⁺ samples indicating that these phosphors had excellent thermal stability and stable color (no emission shift). All these properties indicate that the developed phosphors may be potentially used as single‐component color‐tunable‐emitting phosphors for UV light‐emitting diodes.     

Ionic liquid-assisted two-phase synthesis of Lu7O6F9:Yb3+, Er3+ phosphors and their morphological control,color-tunable up-conversion luminescence and temperature sensing behavior

In this work, Lu₇O₆F₉ microcrystals with various novel morphologies, including hand broom-like nanorods, nanoparticles, hexagons, spindle-like nanoparticle aggregates, hexagonal prisms and microrods, were prepared via ionic liquid-assisted two-phase method and following calcination approach. Ionic liquid was used as F^? resource, morphology controller and two-phase solvent. The effect of preparation condition on the phases and morphologies of the precursors as well as the calcined products was studied in detail. The crystallographic structure of Lu₇O₆F₉ was also confirmed by the down-conversion (DC) spectra of Lu₇O₆F₉: Eu³⁺ phosphor with Eu³⁺ ion as the structure probe. Besides, different concentration of Yb³⁺ ions were introduced to the host to obtain Lu₇O₆F₉: Yb³⁺, Er³⁺ phosphors, in case of subsequent investigation on the up-conversion (UC) luminescence properties, UC mechanism and followed temperature sensing behavior. Color-tunable UC emissions were realized and the mechanism was discussed. Furthermore, the optical temperature sensing behavior of orthorhombic Vernier lutecium oxyfluoride was investigated for the first time. The influence of Yb³⁺ content on the sensing sensitivity was also elaborated. These results imply that the as-prepared Lu₇O₆F₉: Yb³⁺, Er³⁺ phosphors could be considered as candidates in color-tunable displaying and optical thermometers.     

Energy Transfer Study on Dense Eu3+/Tb3+‐Coactivated Oxyfluoride Borogermanate Scintillating Glasses

Tb³⁺‐, Eu³⁺‐activated, and Eu³⁺/Tb³⁺‐coactivated oxyfluoride borogermanate scintillating glasses with the density of about 6.50 g/cm³ were successfully synthesized by a melt‐quenching method. The structure and optical properties including transmittance, photoluminescence (excitation and emission spectra), photoluminescence decay, and X‐ray excited luminescence behaviors were studied in detail. Our results reveal that the energy‐transfer efficiency from Tb³⁺ to Eu³⁺ ions increases with an increase in Eu³⁺ concentration. The energy‐transfer mechanism is also discussed by Dexter's and Reisfeld's semiexperimental methods.     

Molecular‐Like Ag Clusters and Eu3+ Co‐Sensitized Efficient Broadband Spectral Modification with Enhanced Yb3+ Emission

AgNO₃/EuF₃/YbF₃ tri‐doped oxyfluoride glass was prepared by a melt‐quenching method, in which a high‐efficient broadband spectral modification can be realized due to the simultaneous energy‐transfer processes of Eu³⁺→Yb³⁺, molecular‐like Ag (ML‐Ag) clusters→Yb³⁺, and ML‐Ag clusters→Eu³⁺→Yb³⁺. The spectral measurements indicated that besides the F‐center brought by the fluorides, the formation of the ML‐Ag clusters and the evolution of silver species within the glass matrix were also closely related to the introduction of Eu³⁺ and Yb³⁺ ions and which in return greatly affected the luminescence properties of these rare‐earth ions. As the UV‐visible irradiation in the wavelength region of 250–600 nm can be efficiently converted into near‐infrared emission around 1000 nm in the AgNO₃/EuF₃/YbF₃ tri‐doped glass, which thus has promising application in enhancing the photovoltaic conversion efficiency of the silicon solar cell.     

Structure and Luminescence Characteristics of Eu3+‐Activated Trigonal Layered Perovskite Ba2La2ZnW2O12

Eu³⁺‐doped tungstate Ba₂La₂ZnW₂O₁₂ phosphors with perovskite‐structure were prepared by the high temperature solid‐state reaction. The X‐ray powder diffraction (XRD) patterns and structure refinements indicate that the phosphors crystalized in the trigonal layer‐perovskite. The luminescence properties of the phosphors were investigated such as photoluminescence (PL) excitation and emission spectra, decay lifetimes, and color coordinates. It was found that the pure host shows self‐activated emission excited by the UV light. Moreover, Ba₂La₂ZnW₂O₁₂ also shows scintillation characteristics under the X‐ray irradiation. The near‐UV and blue light can efficiently excite Eu³⁺‐doped Ba₂La₂ZnW₂O₁₂ phosphors inducing the strong orange–red luminescence. The optimal Eu³⁺ doping concentration in this host is 40 mol%. The luminescence spectra and the luminescence color of the phosphors strongly depend on the doping levels and excitation wavelength. The different luminescence features were discussed on the base of crystal structure. Eu³⁺ ions have two possible substitutions on A or B sites in this trigonal layered perovskite. The phosphor could act as a candidate for the potential application in near‐UV excited white‐LEDs lighting.     

Enhanced luminescence properties of Eu3+ in La2MoO6 by nonsensitization of Bi3+

It was unusual for Bi³⁺ ions to enhance the emission intensity of phosphors via nonsensitization. Here, La₂MoO₆:Eu³⁺, Bi³⁺ phosphors were successfully synthesized by a high temperature solid-state reaction method in air atmosphere. As the increase of doping concentration of Bi³⁺, the emission spectra of La₂MoO₆:Eu³⁺, Bi³⁺ phosphors had obvious shifts, splits and the enhancement of intensities, which indicated that the characteristics of the phosphors were modified. To analyze these phenomena, the crystal structure refinements, spectral characteristic analyze and Judd-Ofelt theoretical calculation were mainly performed. Bi³⁺ ions played the role of the nonsensitizer and affected the distortion of the crystal, the sites of Eu³⁺ ions, the field splitting energy and the internal quantum yield. Moreover the nephelauxetic effects of Bi³⁺ ions and the ET process caused synergistically the life times of La₂MoO₆:Eu³⁺, Bi³⁺ phosphors to increase and then gradually decrease. The CIE coordinates of phosphors changed within a small range. This study might be instrumental in promoting the further application of Bi³⁺ ions in rare earth luminescent materials.     

Synthesis and Persistent Luminescence Mechanism of a Novel Orange Emitting Persistent Phosphor Sr5(BO3)3Cl:Eu2+

A series of Eu²⁺‐doped Sr₅(BO₃)₃Cl phosphors were prepared successfully using a conventional solid‐state reaction method. The luminescent properties were studied systematically by utilizing photoluminescence spectra, decay curves, persistent luminescence spectra, and thermoluminescence glow curves. Energy transfer from host to emission center Eu²⁺ was affirmed. The orange persistent luminescence emission was observed for the first time. The optimal doping concentration of Eu²⁺ for persistent luminescence was experimentally to be approximately 0.5% and the orange persistent luminescence duration can persist about 15 min. On the basis of the experimental results, a model was constructed and the relevant mechanism of persistent luminescence was illustrated in detail. Two different ways of trapping the charge carriers were also discussed.     

Synthesis,energy transfer mechanism,and tunable emissions of novel Na3La(VO4)2:Re3+ (Re3+ = Dy3+, Eu3+, and Sm3+) vanadate phosphors for near-UV-excited white LEDs

In this study, novel Eu³⁺-, Dy³⁺-, and Sm³⁺-activated Na₃La(VO₄)₂ phosphors were synthesized using a solid state reaction method. X-ray diffraction analysis results indicated that the Na₃La(VO₄)₂ phosphors had an orthorhombic crystal structure with the Pbc21 space group. There were two different La(1)O₈ and La(2)O₈ polyhedra with high asymmetry in the crystal structure. Scanning electron microscopy revealed that the product had a sheet morphology with an irregular particle size. Further, the luminescence properties, including the excitation and emission spectra, and luminescence decay curve, were investigated using a fluorescence spectrometer. The results showed that the Na₃La(VO₄)₂ compound was an excellent host for activating the luminescence of Eu³⁺ (614 nm), Dy³⁺ (575 nm), and Sm³⁺ (647 nm) ions. Further, Dy³⁺/Eu³⁺ co-doped Na₃La(VO₄)₂ phosphors were exploited, and the energy transfer from Dy³⁺ to Eu³⁺ was demonstrated in detail by the photoluminescence excitation, photoluminescence spectra, and luminescent decay curves. The results showed that the energy transfer efficiency from Dy³⁺ to Eu³⁺ was highly efficient, and the energy transfer mechanism was dipole–dipole interactions. Finally, tunable emissions from the yellow region of CIE (0.3925, 0.4243) to the red region of CIE (0.6345, 0.3354) could be realized by rationally controlling the Dy³⁺/Eu³⁺ concentration ratio. These phosphors may be promising materials for the development of solid-state lighting and display systems.     

A novel strategy to achieve NaGdF4:Eu3+ nanofibers with color‐tailorable luminescence and paramagnetic performance

Luminescent‐magnetic bifunctional NaGdF₄:Eu³⁺ nanofibers were fabricated through the bond of electrospinning followed by calcination with fluorination technology for the first time. The structure, morphologies, luminescence, and magnetism of nanofibers have been characterized using various techniques. X‐ray diffraction measurement indicates that NaGdF₄:Eu³⁺ nanofibers are hexagonal phase. Scanning electron microscope measurement shows that the mean diameters of electrospinning‐made polyvinyl pyrrolidone/[NaNO₃+Gd(NO₃)₃+Eu(NO₃)₃] composite nanofibers and NaGdF₄:Eu³⁺ nanofibers are, respectively, 428±4 and 231±4 nm under the confidence level of 95%. Under 274‐nm ultraviolet light excitation, NaGdF₄:Eu³⁺ nanofibers exhibit characteristic ⁵D_3,2,1,0→⁷F_J emissions of Eu³⁺ and the tendency of color tones of samples varies from blue, cold white, warm white to red via varying Eu³⁺ content. In addition, samples exhibit paramagnetic features and the magnetic properties of NaGdF₄:Eu³⁺ nanofibers are tailorable by modulating the doping concentration of Eu³⁺. More importantly, the color‐tailorable luminescence and paramagnetic properties are simultaneously realized in single‐phase NaGdF₄:Eu³⁺ nanofibers, which ideally suit to apply in many fields such as lighting and color displays, bioimaging, and magnetic resonance imaging. This design conception and construction strategy may provide some new guidance for synthesizing other rare‐earth fluorides nanomaterials of multifarious morphologies.     

Eu2+, Dy3+: Sr2B5O9Cl,a new blue-emitting phosphor with long persistence

A new Eu²⁺, Dy³⁺: Sr₂B₅O₉Cl phosphor with long persistence was synthesized in a reducing atmosphere by a solid-state reaction process. The pure-phase phosphor was obtained by calcination at 900 °C. The introduction of Eu²⁺ into the lattice of the matrix resulted in a broad blue emission centered at 423 nm, which was due to the characteristic 4f6⁵d¹ to 4f⁷ energy transfer of Eu²⁺ ions. Both Eu-doped and Dy/Eu-codoped phosphors displayed afterglow behaviors due to the electron traps generated by the incorporation of tri-valanced rare earth cations into the original Sr lattice sites. The afterglow of Eu²⁺: Sr₂B₅O₉Cl and Eu²⁺, Dy³⁺: Sr₂B₅O₉Cl phosphors showed standard double exponential decay behaviors, and the Eu²⁺/Dy³⁺ co-doped sample demonstrated better afterglow properties than Eu²⁺-doped one. A longer lifetime for the electrons was confirmed after the afterglow decay curve simulation. Based on the analysis of thermally stimulated luminescence (TSL), the difference in afterglow was attributed to the different trap concentrations induced by the Dy³⁺ (Eu³⁺) doping in the Sr₂B₅O₉Cl matrix.     

Deep blue,cyan, orange-red,and white multicolor emissions generated by Bi3+/Eu3+ activated KBaYSi2O7 luminescent materials for white light-emitting diodes

A variety of Bi³⁺ and/or Eu³⁺ doped KBaYSi₂O₇ phosphors with deep blue, cyan, orange-red, and white light multicolor emissions have been fabricated by a Pechini sol-gel (PSG) method. The KBaYSi₂O₇:Bi³⁺ phosphors exhibit an intense cyan emission or a unique narrow deep blue emission when excited by different wavelengths, which may bridge the cyan gap or act as a promising deep blue phosphor for white light-emitting diodes (WLEDs). The tunable multicolor emissions can be achieved by changing the Bi³⁺ doping concentrations. The Bi³⁺/Eu³⁺ co-doped KBaYSi₂O₇ phosphors display intrinsic emissions of Bi³⁺ and Eu³⁺ and an energy transfer process between Bi³⁺ and Eu³⁺ can be detected. The luminescence colors of KBaYSi₂O₇:Bi³⁺,Eu³⁺ regularly shift from blue, through cold and warm white, finally toward orange-red by adjusting the relative doping concentrations of Bi³⁺ and Eu³⁺. The single-phase white light-emitting material can be generated in both cold and warm white regions by simply varying the Eu³⁺ doping concentrations. Furthermore, three kinds of WLEDs devices are fabricated by KBaYSi₂O₇:Bi³⁺ or KBaYSi₂O₇:Bi³⁺,Eu³⁺ phosphors, which can exhibit dazzling white light emissions with eminent CIE coordinates, correlated color temperature, and color rendering index. The result offers direct evidence that the as-synthesized phosphors may be potentially applied in WLEDs and solid-state lighting.     

Strong f–f excitation in hafnium germanate: Near-UV LED and cathode beam–pumped red phosphor with thermal robustness

Developing narrowband red phosphors has always been a frontier topic in the phosphor community. In this study, a novel hafnium germanate red phosphor, BaHfGe₃O₉:Eu³⁺, was successfully synthesized by solid-state reaction method. The phase and crystal structure of BaHfGe₃O₉ were investigated by the Rietveld refinement of powder X-ray powder diffraction. The band structure was analyzed by density functional theory calculations. Most importantly, the luminescence behavior of phosphors under near-ultraviolet (n-UV) light and cathode rays sources was studied in detail to explore the possibility of their applications in white light-emitting diodes and field emission display. The BaHfGe₃O₉:Eu³⁺ phosphor exhibits strong f–f excitation and excellent thermal robustness due to Eu³⁺ localization in the rigid lattice and asymmetric Ba²⁺ sites. Under cathode rays and n-UV light excitation, BaHfGe₃O₉:Eu³⁺ exhibits narrowband red light emission peaked at 610 nm. Moreover, BaHfGe₃O₉:Eu³⁺ shows excellent saturation resistance and aging resistance. The performance of the LED lamp encapsulated by the BaHfGe₃O₉:Eu³⁺ phosphor was studied. The results show that BaHfGe₃O₉:Eu³⁺ is a potential red phosphor for multifunctional applications.     

Reveal luminescence differences via comparative studies of dynamic spectra in Eu3+-activated BaLa2WO7 and SrLa2WO7 phosphors

Eu³⁺-doped BaLa₂WO₇ and SrLa₂WO₇ phosphors were prepared using the conventional solid-state reaction synthesis. The experiments have confirmed that the luminescence properties are completely different although they the isostructural monoclinic structure with a monoclinic space group of P21/b: compared with SrLa₂WO₇:Eu³⁺, BaLa₂WO₇:Eu³⁺ has stronger luminescence and higher thermal stability. The dynamic characteristics were studied via the laser site-selective excitation and luminescence technique. The two distinct Eu³⁺ centers Eu³⁺(A) and Eu³⁺(B) were confirmed corresponding to the substitution for La1 and La2, respectively. Eu³⁺(A) could transfer energy to Eu³⁺(B) in BaLa₂WO₇:Eu³⁺, but Eu³⁺(B) cannot realize back transfer to Eu³⁺(A). However, a mutual energy transfer could be achieved between Eu³⁺(A) and Eu³⁺(B) in SrLa₂WO₇:Eu³⁺ resulting in excitation energy diffusion. The energy dispersion may cause the excited electrons to be trapped in some defects and impurities, thereby reducing the luminescence effect. The results could help develop new reddish-orange emitting materials by introducing Eu³⁺ as a structural probe for doping sites and microstructure.     

Precipitation Synthesis and Color‐Tailorable Luminescence of α‐Zr(HPO4)2: RE3+(RE = Eu,Tb) Nanosheet Phosphors

The rare earth (RE = Eu and Tb) ions‐doped α‐Zr(HPO₄)₂ (ZrP) nanosheet phosphors were synthesized by direct precipitation method, and their structures and photoluminescence properties were investigated. The results of X‐ray diffraction and scanning electron microscopy indicated that the systems of ZrP:RE³⁺ had similar nanosheet structure except with relatively larger interlayer spacing as compared with pure α‐ZrP. Under the excitation of UV light, the ZrP:RE³⁺ nanosheet phosphors showed red and green emission peaks corresponding to the ⁵D₀→⁷F₂ transition of Eu³⁺ and the ⁵D₄→⁷F₅ transition of Tb³⁺, respectively. After Eu³⁺ and Tb³⁺ were co‐doped in ZrP host, not only the red and green emission peaks were simultaneously observed, but also the luminescent intensity and fluorescence lifetimes of Tb³⁺ were gradually decreased with the increase in Eu³⁺‐doping concentration, which implied the energy transfer from Tb³⁺ to Eu³⁺ happened. It was deduced that the energy transfer from Tb³⁺ to Eu³⁺ occurred via exchange interaction. Through optimization to the samples, a nearly white‐light emission with the color coordinate (0.322, 0.263) was achieved under 377 nm excitation. The ZrP:RE³⁺ nanosheet phosphors may be a potential color‐tailorable candidate for fabricating optoelectronic devices such as electroluminescence panels.     

Synthesis of blue-emitting AlN:Eu2+ spherical phosphors by carbothermal reduction nitridation method

In this study, blue-emitting AlN:Eu²⁺ spherical phosphors were successfully synthesized for the first time by the carbothermal reduction nitridation (CRN) method, assisted with high nitrogen pressure, appropriate synthesis temperature, and the addition of CaF₂. The influence of typical experimental parameters, such as N₂ pressure, heating temperature, CaF₂ content and Eu²⁺ concentration on the morphologies and luminescence properties of AlN phosphors were comprehensively investigated. The formation mechanism of spherical morphology were significantly proffered, indicating that sufficient liquid Ca-aluminates during the AlN growth stage were essential for the spheroidization process under the action of surface tension. The synthesized AlN:Eu²⁺ spherical phosphors presented an intense blue emission band centered in the range of 427- 476 nm relative to the reaction temperature. The lifetime of AlN:Eu²⁺ phosphor was calculated to be around 1.89 μs. The temperature-dependent PL spectra suggested that the emission band did not shift until 225°C. In addition, the spectral analysis strongly suggested that the luminescence property of AlN:Eu²⁺ phosphors was significantly enhanced by the large particle size, spherical morphology, reduced impurity content, and appropriate Eu²⁺ concentration.     

Tunable photoluminescence of nanostructured LaPO4:Eu3+/Tb3+ synthesized via a microwave-assisted ethylene glycol route

Nanostructured phosphors LaPO₄:Eu³⁺/Tb³⁺ were prepared via a combined approach using microwave heating and a bifunctional solvent (ethylene glycol) acting as both microwave absorber and capping agent. The synthesized samples were characterized by X-ray diffraction (XRD), attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), transmission electron microscopy (TEM) and photoluminescence (PL) measurements. All samples crystallized in a monoclinic monazite-type structure. Electron microscopy analysis revealed a hierarchical organization of self-assembled seed crystals of lanthanum phosphate into nanoparticles that, in turn, gave rise to sponge-like aggregates. The co-doped samples exhibited self-activated blue luminescence from the host matrix, as well as red and green emissions due to the presence of Eu³⁺ and Tb³⁺ ions, respectively. Furthermore, the spectroscopic analysis indicated energy transfer from terbium to europium ions.The synthetic route described here is efficient to prepare nanomaterials with advanced optical properties, which exhibit a potential for applications in photonics, sensing and biolabelling.