Obtain full visible spectrum light-emitting diode illumination via bismuth-activated cyan phosphors

Developing highly efficient cyan-emitting fluorescent materials is essential to bridge the cyan gap in phosphor-converted white light-emitting diodes for full-spectrum white illumination. Here, a Bi-doped cyan phosphor has been reported to solve this gap. The phase purity, photoluminescence emission/excitation spectra, concentration quenching, lifetime decay curves, and temperature-dependent photoluminescence emission spectra were systematically investigated. SrLaGaO₄:Bi³⁺ exhibits a broad excitation band (250–400 nm), which matches with the emission of a commercial near-ultraviolet light-emitting diode chip. The cyan light peaked at 475 nm is observed, which is attributed to the ³P₁→¹S₀ transition of Bi³⁺. The thermal quenching experiment was performed, and the activation energy was calculated as 0.36 eV. Finally, full-spectrum white light-emitting diode devices were fabricated using SrLaGaO₄:Bi³⁺ phosphors, commercial blue BaMgAl₁₀O₁₇:Eu²⁺ phosphor, green (Ba, Sr)₂SiO₄:Eu²⁺ phosphor, and red CaAlSiN₃:Eu²⁺ phosphor, which displayed an International Commission on an illumination coordinate of (0.3732, 0.3850), a correlated color temperature of 4290 K, and a color rendering index of 93.2 at a drive current of 20 mA. This result indicates that SrLaGaO₄:Bi³⁺ plays an essential role in bridging the cyan gap, providing new inspiration for applying cyan-emitting phosphors in full-spectrum white lighting.     

Vacuum Ultraviolet Excited Photoluminescence Properties of Y2O2S：Eu^3＋,Bi^3＋ Phosphor

As an Hg-free lamp using phosphor, the Bi^3＋ and EH^3＋ co-doped Y2O2S phosphors were prepared and their luminescence properties under vacuum ultraviolet（VUV） excitation were investigated. The VUV photoluminescent intensity of Y2O2S：Eu^3＋ was weak, however, considerably stronger red emission at 626 nm with good color purity was observed in Y2O2S：Eu^3＋,Bi^3＋ systems. Investigation on the photoluminescence reveals that the strong VUV luminescence of Y2O2S：Eu^3＋,Bi^3＋ at 147 nm is mainly because the Bi^3＋ acts as a medium and effectively performs the energy transfer process： Y^3＋-O^2-→Bi^3＋→Eu^3＋, while the intense emission band at 172 nm is attributed to the absorption of the characteristic ^1So-^1P1 transition of Bi^3＋ and the direct energy transfer from Bi^3＋ to Eu^3＋. The Y2O2S：Eu^3＋,Bi^3＋ shows excellent VUV optical properties compared with the commercial （Y,Gd）BO3：Eu^3＋. Thus, the Y2O2S：Eu^3＋,Bi^3＋ can be a potential red VUV-excited candidate applied in Hg-free lamps for backlight of liquid crystal display.     

Sr7Zr(PO4)6∶xEu2+蓝色荧光粉的合成及其发光特性

通过高温固相反应合成了新型的蓝色荧光粉Sr₇Zr(PO₄)₆∶xEu²⁺。通过X射线粉末衍射(XRD)、紫外可见(UV-Vis)吸收光谱、荧光光谱研究了Sr₇Zr(PO₄)₆∶xEu²⁺材料的相纯度及荧光性质。结果表明,Eu²⁺掺杂获得的Sr₇Zr(PO₄)₆∶xEu²⁺荧光粉为纯相,且200~400 nm范围内的近紫外(NUV)光均能对其进行有效的激发。在315 nm的激发下,Sr₇Zr(PO₄)₆∶xEu²⁺荧光粉发射出峰值位于415 nm左右的蓝光,且Eu²⁺在Sr₇Zr (PO₄)₆基质中的最佳掺杂浓度为0.05,相应的CIE色度坐标为(0.164,0.021),比商用BaMgAl₁₀O₁₇∶Eu²⁺(BAM)蓝色荧光粉具有更高的色纯度。     

Ca[B8O11(OH)4] : Eu2+ – A Highly Efficient Deep Blue-Emitting Phosphor Prepared by Low-Temperature Self-reduction

Highly efficient inorganic phosphors are crucial for solid-state lighting. In this paper, a new method of low-temperature self-reduction was used for preparing a highly efficient deep blue-emitting phosphor of Ca[B₈O₁₁(OH)₄] : Eu²⁺ (CBH : Eu²⁺). The crystal structure, morphology, chemical state, and photoluminescence (PL) properties of the CBH : Eu²⁺ phosphor have been investigated. By using the screened hybrid function (HSE06), the band gap (E_g) of CBH was calculated to be 7.48 eV, which is a necessary condition for achieving high quantum yield phosphors. The experiment results show that almost all the added raw materials of Eu³⁺ can be reduced to Eu²⁺ in CBH crystal under a non-reducing atmosphere. The CBH : Eu²⁺ phosphor shows a broad excitation spectrum centered at 277 and 327 nm in the range of 220 to 400 nm, and a narrow-band emission spectrum centered at 428 nm in the range of 400 to 500 nm, with a full width at half maximum (fwhm) of 42.35 nm. Under UV radiation, the CBH : 2 %Eu²⁺ exhibits high photoluminescence quantum yield (PLQY=95.0 %), high external quantum efficiency (EQE=31.1 %), and ultra-high color purity (97.6 %). The PL intensity of CBH : 2 %Eu²⁺ remains 62.6 % of the initial intensity at 150 °C. Finally, the white light-emitting diodes (WLED) fabricated by CBH : 2 %Eu²⁺, excited by a 365 nm chip, presents outstanding performances with a luminous efficacy (LE) of 13.9 lm/W, a color rendering index (CRI) of 89.4, and a correlated color temperature (CCT) of 5825 K. The above results show that CBH : Eu²⁺ can be used as a promising blue phosphor for WLED. This new method of low-temperature self-reduction can be applied to design and prepare other new types of highly efficient phosphors.     

High sensitivity and multicolor tunable optical thermometry in Bi3+/Eu3+ co-doped Ca2Sb2O7 phosphors

Currently, with increasing demand for non-contact fluorescence intensity ratio-based optical thermometry, a novel phosphor with high-efficiency, dual-emitting centers, and differentiable temperature sensitivity is more and more urgent to develop. In this work, an efficient dual-emitting center optical thermometry with high sensitivity and multicolor tunable in Ca₂Sb₂O₇:Bi³⁺, Eu³⁺ phosphor is firstly designed and successfully prepared. Under 330 nm excitation, the fabricated phosphor presents the featured and distinguishable emissions of Bi³⁺ and Eu³⁺ ions. The high efficiency energy transfer from Bi³⁺ to Eu³⁺ ions is proved and its corresponding mechanism belongs to dipole-dipole interaction. By modulating the ratio of Bi³⁺/Eu³⁺, the multicolor changes from blue to pink are realized. Based on the discriminative thermal quenching behavior between Bi³⁺ and Eu³⁺, the fluorescence intensity ratio of Eu³⁺ to Bi³⁺ in Ca₂Sb₂O₇ samples illustrates excellent optical thermometry performance from 298 to 523 K. The maximum absolute sensitivity (S_a) and relative sensitivity (S_r) reach as high as 0.2773 K^?1 at 523 K and 2.37% K^?1 at 448 K, respectively. Notably, the discriminated surrounding temperature can be directly confirmed by observing the emitting color from purple to orange-red with the temperature increase from 298 to 523 K. Furthermore, the as-prepared phosphor materials also demonstrate outstanding repeatability and excellent reversibility. These results exhibit that the designed Ca₂Sb₂O₇:Bi³⁺, Eu³⁺ phosphors have great promising applications in the field of non-contact optical temperature thermometry and thermochromic.     

Tunable luminescence and energy transfer process between Tb3+ and Eu3+ in GYAG:Bi3+, Tb3+, Eu3+ phosphors

A series of Eu³⁺ ions co-doped (Gd_0.9Y_0.1)₃Al₅O₁₂:Bi³⁺, Tb³⁺ (GYAG) phosphors have been synthesized by means of solvothermal reaction method. The XRD pattern of GYAG phosphor sintered at 1500 °C confirms their garnet phase. The luminescence properties of these phosphors have been explored by analyzing their excitation and emission spectra along with their decay curves. The excitation spectra of the GYAG:Bi³⁺, Tb³⁺, Eu³⁺ phosphors consists of broad bands in the shorter wavelength region due to 4f⁸ → 4f⁷5d¹ transition of Tb³⁺ ions overlapped with 6s² → 6s¹6p¹ (¹S₀ → ³P₁) transition of Bi³⁺ ions and the charge transfer band of Eu³⁺–O^2?. The present phosphors exhibit green and red colors due to ⁵D₄ → ⁷F₅ transition of Tb³⁺ ions and ⁵D₀ → ⁷F₁ transition of Eu³⁺ ions, respectively. The emission was shifted from green to red color by co-doping with Eu³⁺ ions, which indicate that the energy transfer probability from Tb³⁺ to Eu³⁺ ions are dependent strongly on the concentration of Eu³⁺ ions.     

Recent Research Progress of Red Phosphors for PDPs Applications

The commercial vacuum ultraviolet (VUV) red phosphor (Y, Gd)BO₃:Eu³⁺ has low luminous efficiency and poor color purity. Our work aims to overcome this drawback and we mainly devote to investigating the luminescence mechanism, improving the commercial red phosphor, and seeking for new red emitting VUV materials with high efficiency. Based on the investigation of the photoluminescence mechanism of VUV phosphors, both the luminous efficiency and the color purity of (Y, Gd)BO₃:Eu³⁺ are improved. Additionally, a series of novel VUV red phosphors have been developed, such as (Gd,Y)Al₃(BO₃)₄:Eu³⁺ and (La,Gd)P₃O₉:Eu³⁺. This presentation is a review about the recent research progress of red phosphors for plasma displays (PDPs) applications in our group.     

Enhancement of the photoluminescence and long afterglow properties of Ca<Subscript>2</Subscript>MgSi<Subscript>2</Subscript>O<Subscript>7</Subscript>:Eu<Superscript>2+</Superscript> phosphor by Dy<Superscript>3+</Superscript> co-doping

The Ca₂MgSi₂O₇:Eu²⁺ and Ca₂MgSi₂O₇:Eu²⁺, Dy³⁺ long afterglow phosphors were synthesized under a weak reducing atmosphere by the traditional high temperature solid state reaction method. The synthesized phosphors were characterized by powder X-ray diffraction (XRD) and energy dispersive X-ray spectroscopy (EDX) techniques. The luminescence properties were investigated using thermoluminescence (TL), photoluminescence (PL), long afterglow, mechanoluminescence (ML), and ML spectra techniques. The crystal structure of sintered phosphors was an akermanite type structure, which belongs to the tetragonal crystallography. TL properties of these phosphors were investigated, and the results were also compared. Under the ultraviolet excitation, the emission spectra of both prepared phosphors were composed of a broad band peaking at 535 nm, belonging to the broad emission band. When the Ca₂MgSi₂O₇:Eu²⁺ phosphor is co-doped with Dy³⁺, the PL, afterglow and ML intensity is strongly enhanced. The decay graph indicates that both the sintered phosphors contain fast decay and slow decay process. The ML intensities of Ca₂MgSi₂O₇:Eu²⁺ and Ca₂MgSi₂O₇:Eu²⁺, Dy³⁺ phosphors were proportionally increased with the increase of impact velocity, which suggests that this phosphor can be used as sensors to detect the stress of an object.     

Significant enhancement of luminescence intensity of CaTiO3:Eu3+ red phosphor prepared by sol–gel method and co-doped with Bi3+ and Mg2+

In this study, red phosphors Ca_1?n Mg _n TiO₃:Eu³⁺,Bi³⁺ were prepared by the sol?Cgel method and the impact of single dopant, co-dopants and solid solutions on the photoluminescence of the samples has been also investigated. Our results show that the crystal structure of the host does not have distinct changes when doped with Eu³⁺, Bi³⁺ and/or Mg²⁺. The emission intensity at 615?nm of Eu³⁺ increased at the presence of Bi³⁺ ions owing to the energy transfer from Bi³⁺ ion to Eu³⁺ ion. Moreover, with the addition of Mg²⁺, the red emission of the phosphor was further enhanced due to the stronger absorption at 399 and 467?nm, which match well with the emission of near-UV (395?C400?nm) and blue-LED (450?C470?nm), respectively. Under the near-UV (399?nm) or blue light (467?nm) excitation, the fluorescence quantum yield of the optimal composition Ca_0.9Mg_0.1TiO₃:0.18Eu³⁺,0.018Bi³⁺ is 0.36 and 0.41, respectively, which possesses the higher photoluminescence intensity than CaMoO₄:0.2Bi³⁺,0.05Eu³⁺ and the commercially available Y₂O₂S:Eu³⁺ phosphors under near-UV excitation. Based on these results, we are currently considering the potential application of Ca_0.9Mg_0.1TiO₃:Eu³⁺,Bi³⁺ as a near-UV or blue-chip convertible red-emitting phosphor.     

Abnormal Anti‐Quenching and Controllable Multi‐Transitions of Bi3+ Luminescence by Temperature in a Yellow‐Emitting LuVO4:Bi3+ Phosphor for UV‐Converted White LEDs

Phosphors with an efficient yellow‐emitting color play a crucial role in phosphor‐converted white LEDs (pc‐WLEDs), but popular yellow phosphors such as YAG:Ce or Eu²⁺‐doped (oxy)nitrides cannot smoothly meet this seemingly simple requirement due to their strong absorptions in the visible range. Herein, we report a novel yellow‐emitting LuVO₄:Bi³⁺ phosphor that can solve this shortcoming. The emission from LuVO₄:Bi³⁺ shows a peak at 576 nm with a quantum efficiency (QE) of up to 68 %, good resistance to thermal quenching (T_{50 %}=573 K), and no severe thermal degradation after heating–cooling cycles upon UV excitation. The yellow emission, as verified by X‐ray photoelectron spectra (XPS), originates from the (³P₀,³P₁)→¹S₀ transitions of Bi³⁺. Increasing the temperature from 10 to 300 K produces a temperature‐dependent energy‐transfer process between VO₄^3? groups and Bi³⁺, and further heating of the samples to 573 K intensifies the emission. However, it subsequently weakens, accompanied by blueshifts of the emission peaks. This abnormal anti‐thermal quenching can be ascribed to temperature‐dependent energy transfer from VO₄^3? groups to Bi³⁺, a population redistribution between the excited states of ³P₀ and ³P₁ upon thermal stimulation, and discharge of electrons trapped in defects with a trap depth of 359 K. Device fabrication with the as‐prepared phosphor LuVO₄:Bi³⁺ has proved that it can act as a good yellow phosphor for pc‐WLEDs.     

Synthesis and characterization of novel blue emitting Na2CaSiO4:Ce3+ phosphor

The blue phosphors Na_(2?x)Ca_(1?x)SiO₄:xCe³⁺ were synthesized by the sol–gel method and their luminescence characteristics were investigated for the first time. Structural information about prepared samples is obtained by analyzing the XRD patterns and SEM micrographs. The photoluminescence (PL) excitation spectra indicate that the Na_(2?x)Ca_(1?x)SiO₄:xCe³⁺ phosphors can be effectively excited by ultraviolet (360 nm) light. The PL emission spectra exhibit tunable blue broadband emission with the dominant wavelength of 427–447 nm under excitation of 360 nm by controlling the doping concentration of Ce³⁺. The concentration quenching effect for Ce³⁺ was found at the optimum doping concentration of 4 mol%. The Commission Internationale de l’Eclairage 1931 chromaticity coordinates of Na_1.96Ca_0.96SiO₄:0.04Ce³⁺ are (0.1447, 0.0787), which are better color purity compared to the commercial Eu²⁺-doped BaMgAl₁₀O₁₇ phosphor. Na_1.96Ca_0.96SiO₄:0.04Ce³⁺ composition shows intense blue emission (peak wavelength, 439 nm) with relative intensity versus commercial BaMgAl₁₀O₁₇:Eu²⁺ blue phosphor (Nichia) 65 and 158 % under 254 and 365 nm excitation, respectively. All the results indicate that Na_(2?x)Ca_(1?x)SiO₄:xCe³⁺ phosphors are potential candidate as a blue emitting phosphor for UV-converting white light-emitting diodes.     

Synthesis and optical studies of novel Eu2+ and Ce3+ doped BaMg8Al18Si18O72 phosphors

Novel Eu²⁺ and Ce³⁺ activated BaMg₈Al₁₈Si₁₈O₇₂ phosphors was prepared by combustion method and their PL characteristics were investigated. The result shows that all samples can be excited efficiently by near UV excitation under 334 nm and 316 nm. The emission was observed for BaMg₈Al₁₈Si₁₈O₇₂:Eu²⁺ phosphor at 437 nm corresponding to d → f transition, under 334 nm broad-band excitation, whereas BaMg₈Al₁₈Si₁₈O₇₂:Ce³⁺ phosphor shows emission band at 376 nm under 316 nm excitation. Phase purity of the phosphor was checked with the help of XRD pattern. SEM analysis shows the external morphology of the combustion synthesized phosphor.     

Preparation of blue-emitting CaMgSi2O6:Eu phosphors in reverse micellar system and their application to transparent emissive display devices

Blue-emitting Eu²⁺-doped CaMgSi₂O₆ phosphors were prepared by the reverse micelle method. The resultant particles were nanocrystalline with a grain size of about <300 nm and exhibited a characteristic blue emission spectrum centered at 445 nm induced by the oxygen coordinated Eu²⁺ ions. By using the corresponding nanophosphors followed by the formation of a uniform phosphor layer, we have demonstrated the mini-sized transparent plasma-discharge panels and investigated their luminance characteristics. Phosphor coated panel is properly transparent, ≥65%, at the visible wavelength region and illuminates a characteristic blue emission under Ne/Xe plasma discharge conditions. Thus, we can obtain a fast decaying, robust blue-emitting silicate phosphor layer under excited plasma radiation for upcoming emissive display devices like as transparent and three-dimensional plasma display panels.     

Novel high-saturated red-emitting phosphor Sr9(Mg0.5Mn0.5)K(PO4)7: Eu2+ with great quantum efficiency enhancement by La3+ codoping for white LED application

In this work, a novel whitlockite-structure red-emitting phosphor host, Sr₉(Mg_0.5Mn_0.5)K(PO₄)₇, is designed and successfully synthesized via a solid-state reaction. Upon X-ray diffractometer Rietveld refinement, it is revealed that this compound possesses compact Eu²⁺-Mn²⁺ distance (3.6809 Å) and large intra-Mn²⁺ distance (8.9905 Å), which is beneficial to the high-efficient Eu²⁺-Mn²⁺ energy transfer. By Eu²⁺ sensitization, our new phosphor exhibits a high-saturated and bright red Mn²⁺ emission at 620 nm with high color purity of 97.9%. Great emission enhancement up to 245 times than host is achieved by La³⁺ heterovalent substitution, which can be ascribed to the La³⁺-induced further structural confinement effect. Moreover, the quantum efficiency is boosted by twofold. The as-fabricated white phosphor-converted LEDs device shows bright warm white light with correlated color temperature (CCT) of 3,487 K, color-rendering index (CRI) of 92.4, and luminous efficacy of 31.59 lm/W. This work proves the feasibility of chemical unit co-substitution strategy in emission engineering of Mn²⁺-based phosphors, which can stimulate further studies on the red-emitting phosphor materials.     

Photoluminescence Properties of a Promising Red-emitting Phosphor CaNb2O6:EU3+for Trichromatic White Light Emitting Diodes Application

Motivated by the need for new phosphors of white light emitting diode (WLED) application, Ca_0.95Nb₂ O₆:Eu³⁺_0.05 phosphors were synthesized by high temperature solid‐state reaction. Increasing the content of doped‐Eu³⁺ and adding the co‐activator Bi³⁺ to improve the photoluminescence (PL) intensity of Ca_1?xNb₂ O₆Eu³⁺_x phosphors were investigated in detail. The effects of Eu³⁺ were better than that of Bi³⁺ on the PL intensity of Ca_1?xNb₂ O₆Eu³⁺_x phosphors. Compared with Y₂O₂ S:0.05Eu³⁺ the Ca_0.70Nb₂ O₆:Eu³⁺_0.03 phosphor could be excited efficiently by UV (395 nm) light and emit the red light at 614 nm with line spectra, which were coupled well with the characteristic emission from UV‐Near UV LED. The CIE (International Commission on Illumination) chromaticity coordinates (x?0.654, y?0.348) of Ca_0.70Nb₂O₆:Eu³⁺_0.03 were close to the NTSC (National Television Standard Committee) standard values. Therefore Ca_0.70Nb₂ O₆:Eu³⁺_0.03 might find application to UV‐Near UV InGaN chip‐based white light emitting diodes, which is further proved by the LED fabrication with the Ca_0.70Nb₂ O₆:Eu³⁺_0.03 phosphor.     

Synthesis and optical properties of Gd2O3:Pr3+ phosphor particles

Spherical-shaped Gd₂O₃:Pr³⁺ phosphor particles were prepared with different concentrations of Pr³⁺ using the urea homogeneous precipitation method. The resulting Gd₂O₃:Pr³⁺ phosphor particles were characterized by X-ray diffraction, field emission scanning electron microscope, and photoluminescence spectroscopy. The effects of the Pr³⁺ doping concentration on the luminescent properties of Gd₂O₃:Pr³⁺ phosphors were investigated. Photoluminescence measurements revealed the Gd₂O₃:1?% Pr³⁺ phosphor particles to have the strongest emission. The luminescence properties of Gd₂O₃:Pr³⁺ particles are strongly affected by the phosphor crystallinity and X-ray diffraction measurements confirmed that the crystallinity of Gd₂O₃ cubic structure could be enhanced by increasing the firing temperature. The luminescent Gd₂O₃:Pr³⁺ phosphor particles have potential applications in areas, such as optical display systems, lamps and etc.     

Synthesis, vacuum ultraviolet and near ultraviolet-excited luminescent properties of GdCaAl3O7: RE (RE=Eu, Tb)

Vacuum ultraviolet (VUV) excitation and photoluminescent (PL) properties of Eu³⁺ and Tb³⁺ ion-doped aluminate phosphors, GdCaAl₃O₇:Eu³⁺ and GdCaAl₃O₇:Tb³⁺ have been investigated. X-ray diffraction (XRD) patterns indicate that the phosphor GdCaAl₃O₇ forms without impurity phase at 900 °C. Field emission scanning electron microscopy (FE-SEM) images show that the particle size of the phosphor is less than 3 μm. Upon excitation with VUV irradiation, the phosphors show a strong emission at around 619 nm corresponding to the forced electric dipole ⁵D₀→⁷F₂ transition of Eu³⁺, and at around 545 nm corresponding to the ⁵D₄→⁷F₅ transition of Tb³⁺. The results reveal that both GdCaAl₃O₇:RE³⁺ (RE=Eu, Tb) are potential candidates as red and green phosphors, respectively, for use in plasma display panel (PDP).     

Single red up-conversion luminescence of Er sensitized layered Y2Ti2O7 phosphor

High color purity red emission with single band successfully achieved in a new Er³⁺, Tm³⁺ co-doped Y₂Ti₂O₇ system under 1550 nm excitation, value of red to green emission ratio of the samples is more than 10³. Efficient up-conversion luminescence can be obtained while the ⁴I_13/2 level of Er³⁺ pumped by 1500 nm directly based on the large absorption section and long luminescence lifetime, and red emission composition will greatly enhanced by co-doping with Tm³⁺ ions, color purity of red emission under 1550 nm excitation is much higher than that of 980 nm. The quenching concentration of Er³⁺ ions is up to 28 mol% in Y₂Ti₂O₇ rely on the layer distribution of cations, which can further improve the red emission color purity.     

空气中合成固溶体荧光粉Ba2(Zn, Mg)Si2O7:Ce3+,Eu2+,Eu3+及其发光特性

采用高温固相法在空气中合成了Ba_1.97-yZn_1-xMg_xSi₂O₇:0.03Eu,yCe³⁺系列荧光粉。分别采用X-射线衍射和荧光光谱对所合成荧光粉的物相和发光性质进行了表征。在紫外光330~360 nm激发下,固溶体荧光粉Ba_1.97-yZn_1-xMg_xSi₂O₇:0.03Eu的发射光谱在350~725 nm范围内呈现多谱峰发射,360和500 nm处有强的宽带发射属于Eu²⁺离子的4f⁶5d¹-4f⁷跃迁,590~725 nm红光区窄带谱源于Eu³⁺的⁵D₀-⁷F_J (J=1,2,3,4)跃迁,这表明,在空气气氛中,部分Eu³⁺在Ba_1.97-yZn_1-xMg_xSi₂O₇基质中被还原成了Eu²⁺;当x=0.1时,荧光粉Ba_1.97Zn_0.9Mg_0.1Si₂O₇:0.03Eu的绿色发光最强,表明Eu³⁺被还原成Eu²⁺离子的程度最大。当共掺入Ce³⁺离子后,形成Ba_1.97-yZn_0.9Mg_0.1Si₂O₇:0.03Eu,yCe³⁺荧光粉体系,其发光随着Ce³⁺离子浓度的增大由蓝绿区经白光区到达橙红区;发现名义组成为Ba_1.96Zn_0.9Mg_0.1Si₂O₇:0.01Ce³⁺,0.03Eu的荧光粉的色坐标为(0.323,0.311),接近理想白光,是一种有潜在应用价值的白光荧光粉。讨论了稀土离子在Ba₂Zn_0.9Mg_0.1Si₂O₇基质中的能量传递与发光机理。     

Morphology control and luminescence properties of BaMgAl10O17:Eu phosphors prepared by spray pyrolysis

Starting from the aqueous solutions of metal nitrates with citric acid and polyethylene glycol (PEG) as additives, BaMgAl₁₀O₁₇:Eu²⁺ (BAM:Eu²⁺) phosphors were prepared by a two-step spray pyrolysis (SP) method. X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and photoluminescence spectra were used to characterize the resulted BAM:Eu²⁺ phosphors. The obtained BAM:Eu²⁺ phosphor particles have spherical shape, submicron size (0.5-3 μm). The effects of process conditions of the spray pyrolysis, such as molecular weight and concentration of PEG, on the morphology and luminescence properties of phosphor particles were investigated. Adequate amount of PEG was necessary for obtaining spherical particles, and the optimum emission intensity could be obtained when the concentration of PEG was 0.03 g/ml in the precursor solution. Moreover, the emission intensity of the phosphors increased with increasing of metal ion concentration in the solution. Compared with the BAM:Eu²⁺ phosphor prepared by citrate-gel method, spherical BAM:Eu²⁺ phosphor particles showed a higher emission intensity.