Investigations on Valence-Change Behaviors of Europium Ions in Eu-Doped Aluminate and Silicate Phosphors

Compounds of Sr3Al2O6 ： Eu, SrgAl14O25 ： Eu, and BaZnSiO4 ： Eu were synthesized by high-temperature solid state reactions. The doping Eu^3 ＋ ions were partially reduced to Eu^2＋ in Sr4Al14O25：Eu and BaZnSiOg：Eu prepared in an oxidizing atmosphere, N^2 ＋ O2. However, such an abnormal reduction process could not be performed in Sr3Al2O6：Eu, which was also prepared in an atmosphere of N^2 ＋ O2. Moreover, even though Sr3A1EO6：Eu was synthesized in a reducing condition CO, only part of the Eu^3 ＋ ions was reduced to Eu^2 ＋ . The existence of trivalent and divalent europium ions was confirmed by photoluminescent spectra. The different valence-change behaviors of europium ions in the hosts were attributed to the difference in host crystal structures. The higher the crystal structure stiffness, the easier the reduction process from Eu^3 ＋ to Eu^2 ＋ .

Effect of Phosphorus and Fluorine on Hydration Process of Tricalcium Silicate and Tricalcium Aluminate

By means of hydration heat, XRD and SEM, effect of phosphorus and fluorine （P205 and F-） in phosphorous slag on hydration process of tricalcium silicate （C3S） and tricalcium aluminate （C3A） was explored. The results indicated that the early hydration exothermic rate of C3S and C3A was obviously lowered by P205 and F- in phosphorous slag, the second peak occurring time of C3A was delayed by 0.9 h, the exothermal output of C3S was reduced by 25.04% and the time of accelerating stage was postponed by 0.86 h. The early hydration degree of C3S and C3A was also decreased. Due to the influence of P205 and F, more pores and thinner crystals can be observed in the microstructure of hardened paste and the chance of cracks was reduced.

Sol-Gel Synthesis and Luminescent Characteristic of Doped Eu~ 3+ Silicate-Silica Phosphor

Eu-doped silicate complex gel nano-particles was obtained by sol-gel process and characterized with TEM, XRD, PL, etc. The well dispersed particles have particle size about 60 - 70 nm with specific surface area 98.3 m^2· g^- 1 The complex gel phosphor gives a broad and strong luminescent emission originating from Eu^2＋ ions centered at 425 nm. The emission band shifts to shorter wavelengths with the increase of the ion radius of the alkali earth metals, but the band becomes red-shifted gradually with the increase of the ion radius of the alkali metals（except Li ^＋ ）. These divalent Eu^2＋ ions originate in inequivalent substitution of the alkaline earth ions. The presence of alkaline ions is favorable for the increasing emission intensity of the Eu^2 ＋ and lowering crystalline temperature of the silicate complex gel.

Synthesis and Luminescence Properties of Tb^3＋-Activated Silicate Oxyapatite Phosphor

A green-emitting phosphor Ca（Tb1-xLax）4（SiO4）3O （CTLS） was synthesized by a solid state reaction. X-ray diffraction, photoluminescence （PL） spectroscopy, reflectance spectra and chromaticity coordinates were carried out in this study. The CaTb4（SiO4）3O host has been known to crystallize in a hexagonal structure with disordering found in the Ca2＋ and Tb3＋ cation sites. The phosphors exhibited highly green-emitting band centered at 541 nm under ultraviolet excitation, which corresponds to the 5D4→7F5 transition. The optimal doping concentration of Tb3＋ was observed to be at 20 mol%, and the PL intensity was found to decline dramatically when the content of Tb3＋ exceeds 20m01% due to concentration quenching. Based on the results, we are currently evaluating the potential application of Ca（Tb,La）4（SiO4）30 as a new green-emitting near-UV LED convertible phosphor.

Effect of sintering temperature on luminescence properties of borosilicate matrix blue–green emitting color conversion glass ceramics

The color conversion glass ceramics which were made of borosilicate matrix co-doped(SrBaSm)Si2O2N2:(Eu^3+Ce^3+) blue-green phosphors were prepared by two-step method in co-sintering. The change in luminescence properties and the drift of chromaticity coordinates(CIE) of the(SrBaSm)Si2O2N2:(Eu^3+Ce^3+) blue-green phosphors and the color conversion glass ceramics were studied in the sintering temperature range from 600℃ to 800℃. The luminous intensity and internal quantum yield(QY) of the blue-green phosphors and glass ceramics decreased with the sintering temperature increasing. When the sintering temperature increased beyond 750℃, the phosphors and the color conversion glass ceramics almost had no peak in photoluminescence(PL) and excitation(PLE) spectra. The results showed that the blue-green phosphors had poor thermal stability at higher temperature. The lattice structure of the phosphors was destroyed by the glass matrix and the Ce^3+ in the phosphors was oxidized to Ce^4+, which further caused a decrease in luminescent properties of the color conversion glass ceramics.

Luminescence Properties of Green-Emitting Phosphor (Ba_(1-x),Sr_x_2SiO_4∶Eu^(2+) for White LEDS

The （Ba1- x, Srx ） 2 SiO4 ： EU^2＋ green-emitting phosphors were synthesized by conventional solid-state reaction in a CO-reductive atmosphere, and their luminescent properties were investigated. The XRD data show that the Ba/Sr ratio not only affects the lattice parameters, but also influences the emission peak. The excitation spectra indicate that this phosphor can be effectively excited by UV light from 370 to 470 nm. The emission band is due to the 4f^65d^1→4f^7 transition of the Eu^2＋ ion. With an increase in x, the emission band shifts to longer wavelength and the reason was discussed. The emission spectra exhibit a satisfactory green performance under different excitation wavelength（380,398,412,420,460 nm）. （Ba1- x, Srx ） 2 SiO4 ： EU^2＋ is a promising phosphor for green white-lighting-emission diode by ultraviolet chip.

Synthesis and Luminescence Properties of Red Phosphors:Mn^(2+) Doped MgSiO_3 and Mg_2SiO_4 Prepared by Sol-Gel Method

Sol-gel method was utilized to synthesize two different series of red silicate phosphors : MgSiO3 and Mg2SiO4 powder samples doped with Mn2+, conducted the investigation of red long-lasting phosphor: MgSiO3 : Eu2 + , Dy3+, Mn2+ . TGA curves of the gel precursor for two series depicted that the loss of residual organic groups and NO3 groups occurs below 450℃. According to the XRD patterns, the major diffraction peaks of the MgSiO3 and Mg2SiO4 series are consistent with a proto-enstatite structure (JCPDS No.11-0273) and a forsterite structure (JCPDS No.85-1364) respectively. With the excitation at 415 nm, the red emission band of Mn2+ ions is peaked at 661 nm for MgSiO3:1%(atom fraction) Mn2+ or 644 nm for MgiSiO4: 1 %(atom fraction) Mn2+ . Compared with Mg2SiO4:Mn2+ samples, MgSiO3:Mn2+ samples exhibit higher luminescence intensity and higher quenching concentration. In addition, the two series co-doped with Eu2+ , Dy3+ , Mn2+ were also prepared. Photo-luminescence and afterglow properties of the two co-doped series were analyzed, which show that MgSiO3: Eu2 + , Dy3+ , Mn2+ is more suitable for a red long-lasting phosphor.

Synthesis and luminescence properties of Ca_2SiO_4-based red phosphors with Sm^(3+) doping for white LEDs

Sm3＋-activated Ca2SiO4 red phosphors were prepared by the conventional high-temperature solid-state reaction method, and the effects of sodium （Na＋） and samarium （Sm3＋） ions doping concentrations on their crystal structure and luminescent properties were investigated by X-ray diffraction （XRD） and fluorescent spectrofluorometer. XRD patterns demonstrate that a well-crystalline structure forms in the phosphors when they are treated by calcination at 1200~C for 4 h, and the excitation spectra exhibit good absorption in the range between 350 and 420 nm. Under the irradiation of 405 nm near-ultraviolet （NUV） light, the spectra of the phosphors show a main emission peak at 601 nm attributed to the 4G5/2→6H7/2 transition of Sm3＋ ions, and its intensity is greatly influenced by the concentrations of Sm3＋ and Na2CO3. When the concentrations of Sm3＋ ions and Na2CO3 are 2mol% and 6mol%, respectively, the optimal emission intensity can be obtained. From strong absorption in the near ultraviolet zone, the Na0.06Sm0.02Ca1.92SiO4 phosphor is a promising red-emitting phosphor for white light emitting diodes （W-LEDs）.

Photo-luminescence properties and thermo-luminescence curve analysis of a new white long-lasting phosphor: Ca_2MgSi_2O_7:Dy^(3+)

A white long-lasting phosphor Ca2MgSi2O7:Dy3+ was prepared by the solid-state reaction. A strong band peaked at 260 nm was shown in the excitation spectrum of 578 nm emission, which might be attributed to the oxygen deficiency of the host. After irradiated with 254 nm for 4 min, the white afterglow of the sample could be seen for 3 h. Moreover, the depths and frequency factors of trap centers were calculated from the thermo-luminescence curve of the sample, which indicated that the trap centers corresponding to the 414 K band were more helpful to the long-lasting phosphorescence.

Luminescent Properties of Ca2 Y8 ( SiO4 ) 6O2: Eu3 + Phosphors Prepared by Spray Pyrolysis Process

Using CaCO3, metal oxides (all dissolved by nitric acid) and tetraethoxysilane Si (OC2H5 )4 (TEOS) as the main starting materials, Ca2Y8 (SiO4 )6O2: Eu3+ phosphors were synthesized by spray pyrolysis.X-ray diffraction (XRD), scanning electron microscopy (SEM) and photoluminescence (PL) spectra as well as lifetimes were used to characterize the resulting phosphors.The results of XRD indicated that the 1000 ℃ annealed powders crystallize with the silicate oxyapatite structure.SEM study revealed that the phosphors consist of spherical particles with an average size of about 1 ～ 3 μm.In the crystalline Ca2 Y8 (SiO4)6O2: Eu3+ phosphor, the Eu3+ shows its characteristic emission corresponding to 5 D0 - 7 FJ ( J = 0, 1,2, 3, 4) transitions, with 5D0 - 7 F2 red emission (613 nm) as the most prominent group, agreeing well with the structure of the host material.

Exploration of New Phosphors Using a Mineral-Inspired Approach in Combination with Solution Parallel Synthesis

The concept, as well as the methodology of using a mineral-inspired approach in combination with solution parallel synthesis (SPS) for exploration of new phosphors among Na/Sr(Ba)/Al-silicate and Zr(Ti)-silicate minerals, is reported. By employing the proposed approach, we have discovered new phosphors of NaAlSiO4:Eu2+ and BaZrSi3O9:Eu2+, that emit green-yellow (553 nm) and blue-green (480 nm) light, respectively, when excited by radiation of 290 to 420 nm.

共掺La^(3+)和过量Sr^(2+)对荧光粉Sr_(1.96)Eu_(0.04)SiO_4发光性质的影响

采用高温固相法制备了荧光粉Sr_(1.96-x)Eu_(0.04)SiO_(4)∶xLa^(3+)(x=0、0.01、0.02、0.03、0.04、0.05)和Sr_(1.94+y)Eu_(0.04)La_(0.02)SiO_(4)∶ySr^(2+)(y=0、0.05、0.10、0.20、0.30).使用X射线粉末衍射仪、荧光分光光度计表征了荧光粉的物质结构和发光性质.结果表明:荧光粉的XRD均与Sr_(2)SiO_(4)标准卡片PDF 39-1256对应,没有杂质相产生.荧光粉Sr_(1.96)Eu_(0.04)SiO_(4)中掺入La^(3+)能增强其发光强度,且发射峰的位置不变.当La^(3+)掺杂量为2%(摩尔分数)时,荧光粉Sr_(1.94)Eu_(0.04)La_(0.02)SiO_(4)的发光强度最强.在Sr_(1.94)Eu_(0.04)La_(0.02)SiO_(4)中掺入一系列过量浓度Sr^(2+),能增强其发光强度,且不改变发射峰的位置和形状.当Sr^(2+)过量10%时,荧光粉的发光强度最强.荧光粉的宽带发射光谱可以拟合为2个独立的发射峰,对应Eu^(2+)的4f~65d~1→4f~7跃迁,2个发射峰的强度随着通气量的增大有规律变化,使得荧光粉的发光颜色从绿光区过渡到黄光区.

多功能硅酸铋晶体的生长与掺杂

硅酸铋(Bi_(4)Si_(3)O_(12),BSO)晶体是重要的闪烁材料,具有较快的衰减时间、适中的熔点和密度、原料成本低等优势。掺杂不仅能够提高BSO晶体闪烁性能,还可以使其成为多功能材料,比如荧光晶体、激光晶体。总结了BSO晶体的主要研究进展,采用坩埚下降法成功生长了大尺寸BSO晶体,浓度3%以上的稀土掺杂能有效抑制组分偏析;稀土掺杂BSO晶体是导热性能良好的荧光发光材料,紫外光激发下Dy掺杂BSO晶体发黄光,Dy/Tm共掺BSO晶体可实现白光LED发光;研究了Yb、Er、Ho、Tm等稀土掺杂BSO晶体的光谱特性,在Ho:BSO、Tm:BSO晶体中分别实现了0.73 W、0.65 W的激光输出;纯BSO晶体是以Bi3+为发光中心的闪烁晶体,微量Dy掺杂可使BSO晶体光输出提高50%,1%Ta掺杂也能显著提高光输出;BGSO混晶也具有闪烁、激光等发光性能,通过调节组分可以开发出梯度闪烁晶体,稀土掺杂BGSO还可能成为激光晶体。

To tune europium valence by controlling the composition in diphase silicate phosphors

Commercial phosphors always require fewer impurities and higher crystallinity, but sometimes it is difficult or strict to synthesize a pure phase compound. Indeed, if the practical application is not influenced, it is acceptable to synthesize a kind of phosphors with diphase matrix that have similar structure and photoluminescence properties. In present work, we designed and synthesized a series of（1-x）BaMSiO4·xBa2 MSi2 O7：Eu（M = Zn2＋, Mg2＋） diphase phosphors which contained two phases BaMSiO4（hexagonal, P63） and Ba2 MSi2 O7（monoclinic, C2/c） by a high temperature solid-state reaction in air condition. The structures and luminescence properties related to the phase transform from BaMSiO4 to Ba2 MSi2 O7 were analyzed carefully. The results show that the self-reduction ability of Eu3＋ is not the best in above four compounds, respectively. But it reaches the maximum and gets the green emission under the UV lamp when the matrix is in a proper ratio of two phases, which suggests that the heterostructure between the two crystals（BaMSiO4 and Ba2 MSi2 O7） improves the self-reduction process of the diphase.The possible mechanism of the tunable europium valence and the luminescent properties in（1-x）BaMSiO4·xBa2 MSi2 O7：Eu phosphors were discussed in detail.

硅酸盐单基质白光LED荧光体的制备和光谱性质(英文)

用喷雾热解溶胶凝胶方法制备了平均粒径为4.45μm大小的同一基质Ba3MgS i2O8∶Eu2+,Mn2+三色发射合成白光的LED荧光体,研究了掺杂铝离子对荧光体的微结构和发射光谱的影响。实验发现,在375 nm的激发下,红绿蓝(RGB)三种颜色峰的位置分别是608,500,437 nm。微量A l离子的掺入会使荧光粉蓝光和绿光的相对强度发生明显变化,而红光的强度基本不变。因此,荧光体的色坐标位置可以通过掺入不同数量的铝离子来调控。从微结构机制上讨论了铝离子对基质离子的配位、格位和能量状况、发射光谱影响的内在规律。该稀土硅酸盐基质表现出的RGB三色发射特征,可成为重要的新型白光荧光体材料。

白光LED用碱土金属硅酸盐荧光粉的光谱性质

采用固相法合成了A:(SrBa)3SiO5:0.024Ce3+,0.024Li+;B:Sr2.73M0.2SiO5:0.07Eu2+(M=Ba,Mg,Ca);C:(SrBa)3SiO5:xEu2+三个系列的硅酸盐荧光粉。测量了它们的激发光谱和发射光谱。Ce3+激活的硅酸盐荧光粉(A系列)有351,418nm两个激发峰,418nm这个峰较强。随着Ba离子含量的增加,发射光谱峰值波长出现了红移。因此,改变Ba离子的含量,可以改变荧光粉的发射峰值波长,进而调整白光LED的色坐标和显色指数等指标。Eu2+激活的硅酸盐荧光粉(B,C系列)激发光谱是从350～450nm的宽带激发。Ce3+激活的荧光粉发射峰波长要比Eu2+激活的短,在540～555nm左右,而Eu2+激活的发射峰波长在570～583nm范围。在Sr2.73M0.2SiO5:0.07Eu2+系列(B)中,M取Ba时效果较好。在(SrBa)3SiO5:xEu2+系列(C)中,x取不同值发射光谱的峰值波长和半峰全宽有所变化,但是变化的规律不是很明显。用这两种元素作为激活剂的硅酸盐荧光粉均比较适合用于近紫外、紫外和蓝光芯片封装白光LED。在Sr3SiO5:Ce3+,Li+和Sr3SiO5:Eu2+中掺入Ba可以使发射峰红移。

Sr_2SiO_4:Sm^(3+)红色荧光粉的发光特性(英文)

用高温固相法合成了Sr2SiO4:Sm3+红色荧光粉,并研究粉体的发光性质。发射光谱由位于红橙区的3个主要荧光发射峰组成,峰值分别位于 570,606nm和653nm,对应了Sm3+的4G5/2→6H5/2,4G5/2→6H7/2和4G5/2→6H9/2特征跃迁发射,606nm的发射最强。激发光谱表现从350nm到420nm的宽带,可以被近紫外光辐射二极管(near-ultraviolet light-emitting diodes, UVLED)管芯产生的350～410 nm辐射有效激发。研究了 Sm3+掺杂和不同电荷补偿剂对样品发光亮度的影响,Sm3+掺杂摩尔分数为6%、电荷补偿剂为Cl–时的效果最好。Sr2SiO4:Sm3+是一种适用于白光LED的红色荧光粉。

白光LED荧光粉研究及应用新进展

基于白光发光二极管技术的迅速发展以及荧光粉对白光LED器件的发光效率、显色性和使用寿命等性能的决定性影响,系统阐述了蓝光LED芯片激发用铝酸盐、硅酸盐、氮化物和氮氧化物系列黄色、红色和绿色荧光粉的研究进展和应用现状。探讨了上述荧光粉的研究重点、发展趋势和应用前景,指出需要进一步提高铝酸盐黄粉的发光效率,开发新型高光效氮化物和氮氧化物红粉和绿粉及其低成本制备技术,以满足高光效、高显色、低光衰型白光LED器件制作需要。

Eu,Dy共添加的Sr_2MgSi_2O_7基长余辉发光材料

采用高温还原法合成了Sr2 MgSi2 O7∶Eu ,Dy长余辉发光材料 ,并对其性能和余辉机制进行了研究 .实验分析表明 :这种磷光体的主发射峰位于 469nm附近 ,是由于Eu2 + 的 4f5d -4 f跃迁导致的 ;共掺杂的Dy3+ 离子能形成合适深度的能级陷阱 ,从而明显提高余辉性能 .其初始亮度可达 2 2 0 0mcd/m2 ,余辉时间可达

碱磷渣水泥的力学性能及微观结构

研究了以硅酸钠作为激发剂制备的碱磷渣水泥的特点及硅酸钠的模数、掺量和磷渣的比表面积对碱磷渣水泥性能的影响。结果表明:硅酸钠模数为1.2～1.5时碱磷渣水泥的抗压强度最高,并且其抗压强度随着硅酸钠掺量和磷渣比表面积的增加而增大,其后期强度稳定增长。碱磷渣水泥的主要水化产物是水化硅酸钙、方沸石、水化硅铝酸钙。