红色荧光粉Ca2La8Si6O26:Eu的制备和性能

采用高温固相法合成新型CaeLasSi6O26:Eu红色荧光粉,利用X射线衍射、扫描电镜及荧光光谱对其进行了表征.结果表明:合成的Ca2LasSi6O26:Eu属于六角晶系,可被近紫外光(394 nm)和蓝光(464 nm)有效激发,发射峰值位于614 nm(对应于Eu3+的5D0→7F2跃迁),激发波长与目前广泛使用...     

GdF3∶Eu3+和NaGdF4∶Eu3+发光粉的可控合成与发光性质

采用聚乙烯吡咯烷酮(PVP)辅助水热法合成了GdF3∶Eu3+和NaGdF4∶Eu3+发光粉。利用X射线衍射(XRD)、扫描电子显微镜和荧光光谱对样品的结构、形貌和发光性能进行了研究。XRD分析表明:GdF3晶相到NaGdF4晶相的转换可以通过改变初始溶液pH值、PVP加入量和NaF与稀土离子(Gd3+和Eu3+)摩尔配比等合成条件实现。NaGdF4∶Eu3+发光粉的形貌受合成条件的影响。荧光光谱研究表明:GdF3∶Eu3+发光粉主发射峰位于593nm处,来自于Eu3+的5 D0→7 F1磁偶极跃迁;NaGdF4∶Eu3+发光粉主发射峰位于616nm,来自于Eu3+的5 D0→7 F2电偶极跃迁。2个样品中Gd3+与Eu3+离子之间存在较好的能量传递,而NaGdF4晶格更有利于2种离子的能量传递。     

Effect of Calcination Temperature and Concentration on Luminescence Properties of Novel Ca3Y2Si3O12:Eu Phosphors

In the present work, nanocrystalline Ca₃Y_2(1−x)Si₃O₁₂:Eu_x (x=1, 5, 10, and 20 mol%) novel phosphors were synthesized by a sol–gel method. The effect of temperature and concentration on structural and luminescence properties of nanocrystalline powders were investigated under UV excitation. The X-ray diffraction profiles showed that all peaks could be attributed to the orthorhombic Ca₃Y₂Si₃O₁₂ doped Eu phase at the various calcination temperatures with various concentrations. Scanning electron microscopy was carried out to understand the surface morphological features and grain sizes. Photoluminescence (PL) measurements exhibited the presence of all transitions of Eu³⁺ dopant, being the ⁵D₀→⁷F₂ transition the most intense under the charge transfer band and it was observed to be located at around 250 nm. It was also found that, the PL intensity was strongly dependent on both the calcination temperature and dopant concentration. The highest PL intensity was observed for x=5 mol% with temperature at 1000°C. It was observed that the spectral features possess sharp and bright emission for potential applications on the flat panel displays and some other related electronic systems, in observing the images of red color.     

Synthesis,Structure, and Tunable Luminescence Properties of Novel Ba3NaLa(PO4)3F:Eu2+,Mn2+ Phosphors

A series of luminescent emission‐tunable phosphors Ba₃NaLa(PO₄)₃F:Eu²⁺,Mn²⁺ have been prepared by a high‐temperature solid‐state reaction. The Rietveld refinement analysis confirms that the obtained phosphors possess pure apatite crystalline phase and the sites' occupancy of dopant has been also discussed. Upon the excitation of 355 nm, the emission spectra of Ba₃NaLa(PO₄)₃F:Eu²⁺,Mn²⁺ consist of two broad bands assigned to 5d–4f transition of Eu²⁺ and ⁴T₁ (⁴G)–⁶A¹ (⁶S) transitions of Mn²⁺, respectively. Energy transfer (ET) occurs in Eu²⁺, Mn²⁺ codoped Ba₃NaLa(PO₄)₃F host. On the basis of the thorough analysis and comparison upon their excitation, emission properties, and the decay behaviors, it is demonstrated that the ET mechanism between Eu²⁺ and Mn²⁺ is ascribed to the exchange interaction, and the tunable emission color in the novel apatite host can be realized.     

Reaction Synthesis and Mechanical Properties of Lu4Si2O7N2

Crystallized Lu–Si–O–N phases were believed to be the grain‐boundary (GB) phases that might provide Si₃N₄ with excellent high‐temperature mechanical properties. However, little is known about the intrinsic properties, as well as the synthesis, of the Lu–Si–O–N ceramics. This work reveals the reaction paths of heating Lu₂O₃, SiO₂, and Si₃N₄ powder mixtures (with the stoichiometry of 4:0.96:1) from room temperature to 1600°C. Thereafter, dense Lu₄Si₂O₇N₂ samples are synthesized by in situ reaction/hot‐pressing method, and the mechanical properties at room temperature and elevated temperatures are reported for the first time. The Lu₄Si₂O₇N₂ samples show significant high‐temperature mechanical properties, such as the elastic stiffness remains 77% from room temperature to 1500°C; and bending strength keeps 93% from room temperature to 1400°C. The present results shine a light on Lu₄Si₂O₇N₂ as a promising target GB phase for the optimization of high‐temperature mechanical properties of Si₃N₄.     

Combustion Synthesis of Ca2Si5N8: Eu2+ Phosphors and their Luminescent properties

A combustion synthesis method has been developed for synthesis of Eu²⁺‐doped Ca₂Si₅N₈ phosphor and its photoluminescence properties were investigated. Ca, Si, and Eu₂O₃ powders were used as the Ca, Si, and Eu sources. NaN₃ and NH₄Cl were found necessary to be added for the formation of the product phase and addition of Si₃N₄ was found to enhance the product yield. These powders were mixed and pressed into a compact, which was then wrapped up with an igniting agent (Mg + Fe₃O₄). The reactant compact was ignited by electrical heating under a N₂ pressure of 0.7 MPa. Effects of these experimental parameters on the product yield were investigated and a reaction mechanism was proposed. The synthesized Ca₂Si₅N₈: Eu²⁺ phosphor absorbs light in the region of 300–520 nm and shows a broad band emission in the region of 500–670 nm due to the 4f⁶5d¹ → 4f⁷ transition of Eu²⁺. Eu₂O₃ was found partially unreacted and a certain amount of oxygen is believed to be incorporated into the lattice of the product phase. The peak emission intensity (~93% of a commercially available phosphor, YAG:Ce³⁺v) and the peak emission wavelength (571–581 nm) were found to be lower and shorter, respectively, than that reported in the literature. These are considered to be mainly due to oxygen incorporation, which not only reduces nephelauxetic effect and crystal field splitting but also causes a lowering of internal quantum efficiency.     

不同助熔剂对蓝色荧光粉BaMgAl10O17:Eu2+晶体结构颗粒形貌及发光性能的影响

对采用先烧结再还原的高温固相法制备了BaMgAl10O17:Eu2+(BAM)蓝色荧光粉,研究了H3BO3、BaF2、AlF3和MgF24种助熔剂对BAM蓝色荧光粉的物相纯度、粉体颗粒形貌和发光性能的影响.结果表明:添加了助熔剂的样品比未加助熔荆的样晶更有利于BAM的生成,其中H3BO3比BaF2、AIF3、MgF2效...     

Preparation and Luminescence Properties of Eu2+ and Mn2+ Coactivated Tricalcium Phosphate Phosphors

Eu²⁺ and Mn²⁺ coactivated β–Ca₃(PO₄)₂ (TCP) phosphors have been prepared by high‐temperature solid‐state reaction. The site occupation and photoluminescence properties of Eu²⁺ and Mn²⁺ have been identified and discussed in detail. The energy transfer from Eu²⁺ to Mn²⁺ in TCP: Eu²⁺, Mn²⁺ phosphors has been validated and demonstrated to be a resonant type via a dipole‐quadrupole mechanism, and the critical distance (R_C) calculated by concentration quenching method is 21.76 Å. A color‐tunable emission from violet‐blue to red in TCP: Eu²⁺, Mn²⁺ phosphors can be realized via the energy transfer from Eu²⁺ to Mn²⁺ ions.     

Role of Si in the Luminescence of AlN:Eu,Si Phosphors

The luminescence properties of Si,Eu-codoped AlN phosphors were investigated by means of cathodoluminescence. The concentration of Eu was kept constant, while that of Si was varied from 0 to 9.0 at.% using two different Si-source starting powders, Si₃N₄ and SiC. The luminescence of Eu²⁺ in AlN is only observed for samples doped with Si. On the other hand, a concentration quenching is observed for samples doped with high amount of Si from Si₃N₄ while not for those doped from SiC. These results show the importance of Si in the luminescence properties of Eu²⁺-doped AlN.     

Eu~(2+)掺杂SrSi_2O_2N_2和Sr_(0.37)Ba_(0.60)Si_2O_2N_2荧光粉的发光性能及应用

采用高温固相法合成Sr_(0.97)Eu_(0.03)Si_2O_2N_2和Sr_(0.37)Ba_(0.60)Eu_(0.03)Si_2O_2N_2荧光粉,通过X射线衍射、激发光谱、发射光谱及转换后LED器件的性能等研究了荧光粉的结构、发光性能和稳定性。结果表明:在稀土Eu2+掺杂的Sr Si2O2N2荧光粉中,当部分Sr2+被Ba2+取代后,形成三斜晶系的Sr_(0.37)Ba_(0.60)Eu_(0.03)Si_2O_2N_2荧光粉,激发和发射光谱红移,在近紫外-蓝光区具有更高的激发效率。将2种荧光粉与Ga(N)In芯片封装,Sr0.37Ba0.60Eu0.03Si2O2N2荧光粉转换的白光LED器件,在光效、显色指数和光效维持特性方面均高于Sr_(0.97)Eu_(0.03)Si_2O_2N_2转换的LED器件。     

Y2O3：Eu^3＋薄膜的制备及发光性能的研究

以稀土氧化物为原料，用溶胶-凝胶法制备前驱液，加入适量的聚乙烯醇做成膜物质，用浸渍拉提法在石英玻璃表面上得到均匀的薄膜，然后经过适当的干燥和热处理得到Y2O3：Eu^3＋发光薄膜．讨论了Eu^3＋的掺杂浓度和热处理温度对薄膜发光性能的影响．试验表明：Eu^3＋的最佳掺杂浓度为8％（摩尔分数），薄膜的发光性能随热处理温度提高而增强，当热处理温度达到700℃后，薄膜的发光性能基本上稳定．同时用原子力显微镜和X射线衍射分析了薄膜的表面形貌和结构．     

Photoluminescence Mechanism and Thermal Stability of Tb3+‐Doped Y4Si2O7N2 Green‐Emitting Phosphors

With solid‐state reaction method, series of Y₄Si₂O₇N₂:Tb³⁺ phosphors were prepared under the high‐temperature and high‐pressure conditions. The photoluminescence properties at room and high temperature were investigated. Two groups of emission lines have been observed, which are corresponding to Tb^{3+ 5}D₃ → ⁷F_J (J = 6, 5, 4, 3, 2) and ⁵D₄ → ⁷F_J (J = 6, 5, 4, 3) transitions. The physical mechanisms for excitation, emission, concentration quenching, and thermal quenching were investigated. The cross‐relaxation mechanism between the ⁵D₃ and ⁵D₄ emission was investigated and discussed. The Tb–Tb critical distance for cross‐relaxation was calculated to be ~13 Å. The optimum Tb³⁺ concentration in this phosphor is 15 mol%. The quadrupole–quadrupole interaction dominates the non‐radiative energy transfer between the Tb³⁺ luminescence centers and causes the concentration quenching. This phosphor shows high thermal stabilities that at 150°C the intensity remains 92% compared with that measured at room temperature. The present work suggests that this Tb³⁺‐doped Y₄Si₂O₇N₂ material is a kind of potential green‐emitting phosphor.     

Crystal structure of rare-earth silicon-oxynitride J-phases,Ln4Si2O7N2

Rare-earth silicon-oxynitride J-phases, Ln₄Si₂O₇N₂ (Ln=Y, La, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu), were prepared by the N₂ gas-pressured sintering method at 1 MPa of N₂ and 1500–1700 °C. The Rietveld analysis was carried out for X-ray powder diffraction data measured at room temperature. The crystal structures of Ln₄Si₂O₇N₂ were refined with the structure model of La₄Si₂O₇N₂ for Ln=La, Pr, Nd, and Sm, and with that of Lu₄Si₂O₇N₂ for Ln=Y, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. The refined monoclinic unit-cell parameters (lengths a, b, c, angles β, and volume V) increased linearly in their two series of Ln with increasing ionic radii of rare-earth atoms. Discontinuities of the unit-cell parameters were found between the two Ln series.     

Luminescence and structure of Eu2+-doped Ba2CaMg2Si6O17

Eu²⁺-activated Ba₂CaMg₂Si₆O₁₇ phosphors were synthesized by conventional solid-state reaction. The phase formation was confirmed by X-ray powder diffraction measurement. The photoluminescence excitation and emission spectra were investigated. The phosphor presents blue-emitting luminescence. The crystallographic sites of Eu²⁺ ions in Ba₂CaMg₂Si₆O₁₇ host were discussed on the base of luminescence properties and the crystal structure. The lightly Eu²⁺-doped sample shows one luminescence center for the Eu²⁺ ions on Ba²⁺ sites, while there are two luminescence centers for the Eu²⁺ ions on both the Ba and Ca sites in heavily Eu²⁺-doped sample. The dependence of luminescence intensity on temperatures and the activation energy (ΔE) for the thermal quenching were reported. The phosphor shows an excellent thermal stability on temperature quenching because of the special layered structure of Ba²⁺ ions in the interlayer between SiO₄ layers.     

燃烧法合成长余辉发光材料SrAl2O4:Eu2+,Dy3+的研究

以尿素和硝酸盐溶液为反应介质，在600℃下用燃烧法一次制备出了Eu^2 ，Dy^3 掺杂的铝酸锶(SrAl2O4)磷光体。用SEM、XRD研究了所得磷光材料的形态、粒度和物相组成，用荧光分光光度计测定了磷光材料的发光性能。结果表明SrAl2O4：Eu^2 ，Dy^3 磷光材料的晶体结构属于单斜晶系结构。制备产物的形貌呈疏松多孔状，晶粒形状为针状，长度有200nm左右，直径在80nm以下。制备产物在520nm处有很强的发射峰，它的激发光谱是激发峰峰值290nm的宽带激发。并探讨了该材料发光性能的影响因素。     

Synthesis,Crystal and Local Electronic Structures,and Photoluminescence Properties of Red-Emitting CaAlzSiN2+z:Eu2+ with Orthorhombic Structure

Orthorhombic Ca_1−xEu_xAl_zSiN_2+z polycrystalline powders have been synthesized by a solid-state reaction at high temperature in a nitrogen atmosphere. The smaller lattice parameters compared with the single crystal and charge distribution analysis indicate that impure oxygen might be incorporated into the lattice. Ca_1−xEu_xAl_zSiN_2+z shows red emission at about 630 nm due to the transition of 4f⁶5d¹→4f⁷ when excited within 375–450 nm. With an increase in the Eu²⁺ concentration and z, the quantum efficiency of Ca_1−xEu_xAl_zSiN_2+z was significantly decreased due to concentration quenching and high photoionization. First-principle molecular orbital calculations suggest that the overall luminescence of Eu²⁺ may be mainly originated from the small Eu(1) center. CaSiN₂:Eu²⁺ is a potential red conversion phosphor for white LED applications.     

Eu~(3+)掺杂的红色荧光粉制备及荧光性能研究

利用溶胶凝胶法制备了Eu3+掺杂的Y2O3荧光粉。考察了Y2O3:Eu3+的制备条件,进行了物相表征,研究了Y2O3:Eu3+的荧光性能。结果表明,在612 nm波长监测下,Y1.98O3:Eu3+0.02的激发光谱为300~550 nm,最大激发峰值位于466 nm,归属于Eu3+的7F0→5D2的跃迁。在466 nm波长激发下,Y2O3:Eu3+的发射光谱为550~700 nm,最大发射峰值位于612 nm,归属于Eu3+的5D0→7F2的跃迁主峰。Eu3+的掺杂量为x=0.02,p H=1时Y2O3:Eu3+荧光粉可以得到最强的红光荧光粉。     

Gd~(3+)/Si~(4+)掺杂对LiZnPO_4:Eu~(3+)荧光粉发光性能的影响

采用高温固相法制备了LiZnPO4:Eu3+红色荧光粉,分别研究了Eu3+掺量、Eu3+和Gd3+共掺杂以及SiO2掺杂对材料发光性能的影响。结果表明:在395nm近紫外光激发下,发射光谱峰值位于593nm,属于Eu3+的5D0→7F1辐射跃迁;激发光谱由200~280nm的宽带和310~500nm的一系列尖峰组成,分别对应于O2–→Eu3+电荷迁移带和Eu3+的f→f能级跃迁吸收,主激发峰位于395nm左右,与近紫外发光二极管(NUV-LED)的发射光谱(360~410nm)匹配。Eu3+最佳掺杂摩尔分数为12%,超过12%后发生浓度猝灭现象,浓度猝灭机理为电多极–电多极相互作用。掺杂Gd3+、SiO2使Eu3+在593nm处的发射分别增强了107%、105%。LiZnPO4:Eu3+是适合NUV-LED管芯激发的白光发光二极管用高亮度橙红色荧光粉。     

The Effect of Zinc Acetate Dihydrate on Morphology and Luminescence Properties of CaSi2O2N2: Eu2+ Phosphor

CaSi₂O₂N₂: Eu²⁺ phosphors with zinc acetate additive as a flux agent have been synthesized successfully by solid‐state process. The structure, morphology, and photoluminescence (PL) properties of the compounds are investigated as a function of zinc acetate dihydrate (Zn(CH₃COO)₂·2H₂O) dosage. X‐ray diffraction (XRD) measurement indicates that the pure CaSi₂O₂N₂ phase is obtained by adding appropriate amount of zinc acetate dehydrate. The sheetlike morphology of sample transforms into block as Zn(CH₃COO)₂·2H₂O content reaching 43 wt%, associated with the increase in emission intensity. A strong absorption band from near ultraviolet (NUV) to visible range and a broad yellow emission band in the wavelength range of 460–700 nm are observed in Eu²⁺‐doped CaSi₂O₂N₂. High bright yellowish light emitting diodes are obtained by combining CaSi₂O₂N₂:Eu²⁺ as the wavelength conversion phosphor with NUV InGaN LED‐chip (395 nm). The bright yellowish emission and the low thermal quenching effect of CaSi₂O₂N₂: Eu²⁺ with zinc acetate additive make it a potential phosphor converter for white LEDs.