Synthesis of Neodymium-Doped Yttrium Aluminum Garnet (Nd∶YAG) Nano-Sized Powders by Low Temperature Combustion

The homogeneously dispersed, less agglomerated (Nd0.01Y0.99)3Al5O12 nano-sized powders were synthesized by the low temperature combustion (LCS), using Nd2O3, Y2O3, Al(NO3)3·9H2O, ammonia water and citric acid as starting materials. This method effectively solves the problems caused by solid-state reaction at high temperature and hard agglomerates brought by the chemical precipitation method. The powders were characterized by TG-DTA, XRD, FT-IR, TEM respectively and the photoluminescence (PL) spectra of (Nd0.01Y0.99)3Al5O12 green and sintered ceramic disks were measured. The results show that the forming temperature of YAG crystal phase is 850 ℃ and YAP crystal phase appearing during the calcinations transforms to pure YAG at 1050 ℃. The particle size of the powders synthesized by the LCS is in a range of 20～50 nm depending on the thermal treatment temperatures. The effectively induced cross section (σin) with the value 4.03×10-19 cm2 of (Nd0.01Y0.99)3Al5O12 ceramics is about 44% higher than that of single crystal.     

Study on(Y,Gd)3(Al,Ga)5O12∶Ce3+ Phosphor

(Y1-a, Gda)3-x(Al1-b, Gab)5O12∶Ce3 x was synthesized by high-temperature solid state reaction in reducing atmosphere based on high purity raw materials. The influences of Y3 , Gd3 , Al3 , Ga3 and activator-Ce3 on the performance of the phosphor were investigated. Ce3 is the luminescent center and activates the phosphor after it replaces Y partially. When x is less than 0.12, the volume of the crystal and the emission intensity of the phosphor increase with the quantity of Ce3 . When CeO2 is added too much, the phase CeAlO3 will appear. The excitation and emission peaks of the phosphor will shift to longer wavelength when the amount of Gd3 increases. The wavelength of the emission peak can shift about 20 nm when a equals 0.45. In opposite, the excitation and emission peaks will shift to shorter wavelength, when part of Al3 is replaced by Ga3 . The wavelength of the emission peak can shift about 20 nm when b equals 0.55. Through the replacemeat of Y3 or Al3 by Gd3 or Ga3 , the emission peak of the phosphor can be adjusted from 520 to 560 nm. In this way, the phosphor is more suitable for different chips.     

Lattice Parameter Change of Nd∶Gd3Ga5O12 Crystal with Growth Direction

The lattice parameter change of Nd∶GGG crystal was studied by X-ray powder diffraction and the least square fitting method. The results indicate that the lattice parameters of Nd∶GGG increase along the crystal growth direction. By analyzing the Nd∶GGG crystal structure and ions occupying site, the reason of lattice parameter change is mainly attributed to the volatilization of gallium ingredient and lead to the Ga vacancy sites(Oxygen octahedral center) were occupied by Gd3 with large ionic radii, and that the substitute increases with the crystal growth direction. In addition, the Gd sites(oxygen dodecahedron center) were occupied by dopant Nd3 with large ionic radii and the Nd3 distribution coefficient in GGG crystal is smaller than 1, therefore, the substitute also increased with the crystal growth direction, which is another reason led to the lattice parameter increase along the crystal growth direction. In order to decrease the lattice parameter change and improve the crystal quality, some methods were adopted to restrain effectively the Ga2O3 volatilization and decrease the Nd3 concentration change along the crystal growth direction.     

Synthesis of Ce:YAG Phosphor via Homogeneous Precipitation under Microwave Irradiation

Ultra-fine Ce:YAG phosphors were prepared by homogeneous precipitation under microwave irradiation method. The formation of Ce:YAG was investigated by means of XRD and DTA/TG. The purified YAG crystallized phase was obtained at a lower temperature (1100 ℃). Basically spherical Ce:YAG powders were indicated from TEM images, and the size of the particles is about 80 nm. Two peaks of 436 and 473 nm can be seen from the excitation spectrum in the range of 402～510 nm. A broad emission band located at 480～630 nm shows the phosphors prepared by this method have good emission properties.     

用于YAG透明陶瓷的喷雾造粒改性粉体的制备

通过喷雾造粒方法对共沉淀合成的纳米粉体进行改性,制备出球形的纳米颗粒.用XRD对粉体进行物相分析;用TEM观察了改性前粉体的颗粒形状、尺寸大小和团聚情况;用SEM观察改性前后粉体的团聚体的颗粒形状、尺寸大小与分散性,以及陶瓷热腐蚀抛光后的表面形貌.结果表明:PVB添加质量分数1.0%为最优添加量;改性后粉体所制素坯的密度显著提高,从而影响陶瓷的致密度和晶界形貌;经真空烧结制备出相对密度达99.95%的无孔净晶界YAG透明陶瓷,陶瓷晶粒的平均尺寸为10μm左右,尺寸分布较均匀,晶界清晰,晶粒中与晶界处较干净,无杂质与气孔的存在.     

Study on Lattice Parameter Variance and Eutectic Reaction during Crystal Growth of Nd,Cr∶GSGG by Czochralksi Method

During the crystal growth of Nd, Cr∶GSGG by Czochralski method, in some cases eutectic reaction occurred in the nether region of the crystal, and the boule was divided into two obvious different parts, which is upper Nd,Cr∶GSGG crystal and the nether coexisting Nd,Cr∶GSGG and GdScO3. By X-ray powder diffraction, the structure change of NdCr∶GSGG crystal of Φ 27 mm×120 mm with eutectic along its grown direction <111> was studied. By the least square method and extrapolation function f=sinθ-sinθ1-t(t is an adjustable parameter), the lattice parameters of Nd,Cr∶GSGG and additional GdScO3 phase were computed. The results indicate that the lattice parameters of Nd,Cr∶GSGG increase along its growth direction, which changes from a=(1.25650±0.00007) nm of the top to (1.25798±0.00010) nm of the bottom. In the process of Nd,Cr∶GSGG growth, Gd3 in Nd,Cr∶GSGG is partly replaced by Nd3 with larger ionic radii, and the volatilization of Ga component results in its composition variance, which cause the lattice parameters increase along growth direction. In the eutectic section, there are the Nd,Cr∶GSGG and the second phase orthorhombic GdScO3. The lattice parameters of GdScO3 are a=0.5443±0.0007, b=0.5699±0.0005 and c=(0.7865±0.0009) nm, and that of Nd,Cr∶GSGG is (1.25798±0.00010) nm. In the final growth stage, excessive volatilization of Ga composition during the crystal growth causes the growth melt deflect of the Nd,Cr∶GSGG solid solution range seriously, and results in the eutectic reaction, and the outgrowth of Nd,Cr∶GSGG and GdScO3. So it is necessary to decrease the effect of gallium volatilization during the growth in order to avoid eutectic growth and obtain a high-quality Nd,Cr∶GSGG.     

Preparation and Upconversion Luminescence of Y3Al5O12∶Yb3+, Er3+ Transparent Ceramics

YAG:1% (atom fraction) Yb3 , 0.5% (atom fraction) Er3 transparent ceramics were fabricated by the solid state reaction method using high-purity Y2O3, Al2O3, Yb2O3, and Er2O3 powders as starting materials. The mixed powder compact was sintered at 1760 ℃ for 6 h in vacuum and annealed at 1500 ℃ for 10 h in an air atmosphere. The ceramics consisted of about 10 μm grains and exhibited a pore-free structure. The optical transmittance of the ceramics at 1064 nm was nearly 80%. Upconversion emissions were investigated on the ceramics pumped by a 980 nm continuous wave diode laser, and strong green emission centered at 523 and 559 nm and red emission centered at 669 nm were observed, which originated from the radiative transitions of 2H11/2→4I15/2, 4S3/2→4I15/2, and 4F9/2→4I15/2 of Er3 ions, respectively.     

Synthesis of Neodymium-Doped Yttrium Aluminum Garnet (Nd∶YAG) Nano-Sized Powders by Low Temperature Combustion

Transparentpolycrystallineneodymium dopedyt triumaluminumgarnet (Nd0 .0 1Y0 .99) 3 Al5O12 ,Nd∶YAG)ceramics ,laserceramicmatrixmaterials ,withpredominantlychemicalstability ,highlydopedionconcentration ,excellentopticalperformanceandhightemperaturestability ,aregraduallybecomingsubsti tutesforsinglecrystals[1,2 ] .Itisevidentlythathomo geneouslydispersed ,lessagglomeratedandnano sizedprecursorpowdersareextraordinarilyfavorabletoformceramicgreenbodies .Presently ,theconventionallyusedmethods…     

Nd3+对红色荧光粉MgSiO3∶Mn2+,Nd3+发光性能的影响

采用高温固相法制备长余辉发光材料MgSiO3∶Mn2+,Nd3+。借助X射线粉末衍射、激发光谱、发射光谱和余辉衰减曲线对样品进行表征,研究Nd3+对这种红色荧光粉发光性能的影响。结果表明,Nd3+的掺入没有引起样品的晶体结构的变化,但对光谱强度和余辉性能有着显著影响,通过比较单掺Mn2+、单掺Nd3+、双掺Mn2+,Nd3+体系的热释光曲线,揭示了双掺体系中Nd3+的陷阱作用。双掺样品中存在Nd3+向Mn2+能量传递,Nd3+的最佳掺杂量为4%。     

高亮度白光LED用YAG∶Ce~(3+)荧光粉的研制

根据蓝光芯片的发光特性,从激活剂、助熔剂、基质Y3+的替代物等方面较系统地研究了YAG∶Ce3+荧光粉的制备。最终的荧光粉产品制成5mm封装20mA蓝光激发的白光LED后,光效可达70 lm/W,显色指数≥80。     

合成高活性Y_2O_3和Al_2O_3超细粉及Nd:YAG透明陶瓷

分别以Y(NO3)3和氨水、NH4Al(SO4)2·12H2O和碳酸氢铵为原料,采用化学沉淀法与碳酸铝铵分解法合成了高活性、平均粒径分别为39 nm和95 am的Y23和AlO3超细粉体.以Y2O3,Al2O3超细粉和商用Nd2O3粉体为原料,采用固相反应法,经1 700℃真窄烧结15 h,制备了Nd:YAG透明陶瓷.含x(Nd)=1%的YAG陶瓷在可见光区最大透光率约为53%.对YAG陶瓷的烧结过程和显微组织研究表明,Nd的引入明显地促进了陶瓷的烧结,同时晶粒得到细化.     

Kinetics of Fluorescence Decay in Er~(3+)∶YAG under 408.6 nm Excitation

Because trivalent erbium ion doped in opticalhosts has abundant energy structure ,ultraviolet ,visi-ble and infrared fluorescences can be performed .Andmany Er3 +-doped materials have been extensivelystudied on energy levels ,energy transfer , upconver-sionluminescence andlaser actions[1 ~7].Among Er3 +-doped materials ,Er3 +∶YAGis an excellent laser crys-tal for a solid state laser due to its remarkable virtuessuch as chemical stability , durability , UVresistanceas well as good thermal c…     

Preparation of Neodymium-Doped Yttrium Aluminum Garnet Transparent Ceramics by Homogeneous Precipitation Method

Neodymium-doped yttriumaluminumgarnet(Nd∶YAG)transparent polycrystalline ceramics,laser ce-ramic matrix materials,are gradually becomingsubsti-tutes for single crystals because they are provided withpredominantly chemical stability,highly doped ionconcentration,excellent optical performance and hightemperature stability[1,2].Presently,the conventionallyused methods to produce Nd∶YAG powders are solid-state processes[3],chemical precipitation methods[4,5]andlowtemperature combustiontechniqu…     

YAG∶Ce Phosphors for WLED via Nano-Pesudoboehmite Sol-Gel Route

Whitelight emittingdiodes(WLED)arepoised forrevolutionizingtheluminescencelightingindustry,andhavethepotentialofreplacingtheconventionalin candescentanddischarge column typefluorescent lampsforhighefficiency,longlifetime,nopollution,fullsolid statelampetc.Todate,theblueLEDchip combinedwithyellowceriumdopedyttriumaluminum garnetphosphors(YAG∶Ce)isthemostcommonpat terntoproducewhitelight[1].Traditionally,theYAGphosphorispreparedby solid statereactionsusingsolidchemicalsofY2O3and Al2O3ass…     

一种用于铝中超声波取向性测量的激光超声波系统

建立了一种激光超声波系统,用于测定铝样品中产生的超声波的振幅的取向性(角度决定型模式)。脉冲为Nd:YAG的激光工作参数为:光波波长1064nm,典型的8 ns的脉冲宽度(半高峰宽度)、脉冲能量450mJ,该激光脉冲用于在样品中产生超声波。激光探测系统是一种Mach-Zehnder干涉仪,具有典型的0.25nm(rms)噪声限制分辨率,频率范围:50kHz~20MHz,测量范围-75nm/V~+75nm/V。利用两种面积大小不同的Nd:YAG激光光斑在烧蚀区域产生超声波:一种是集中的,另一种是发散的。利用所得到的数据,绘出取向性图形并和理论曲线相比较,显示出良好的一致性。实验结果表明取向性是光斑尺寸大小的函数。对于一个点超声波源(或集中的光斑)的取向性表明,纵向波在所有的方向均显示出相当大的振幅。对于较大超声波源(或发散光斑)的取向性表明,在内部±10°角度左右会产生较大振幅的纵向波。     

Influence of Ambient Gas and Oxygen Pressure on Nd∶LuVO_4 Films Grown by Pulsed Laser Deposition

Influence of Ambient Gas and Oxygen Pressure on Nd∶LuVO_4 Films Grown by Pulsed Laser Deposition     

Crystal Growth and Laser Characteristics of Nd~(3+)∶KGd(WO_4)_2

The solid-state diode-pumped laser was widelyusedin many fields.With the development of crystalgrowth,many good working materials were discov-ered,such as:Nd3+∶YAG,YVO4[1],YLF[2,3],andNd3+∶KY(WO4)2(Nd∶KYW),Yb3+∶KY(WO4)2(Yb∶KYW),Nd3+∶KGd(WO4)2(Nd∶KGW)in recent10years.Compared with Nd∶YAG,Nd∶KGWhas manyoutstanding properties:the emission cross section isbig at the output wavelength of1064and1351nm,concentrate quenching of high Nd3+(at a maxi mumof10%)(atomfraction)is v…     

Zr-Ni中间层对TC4钛合金/304SS不锈钢激光焊接头组织性能的影响

钛合金/不锈钢异种金属焊接结构在现代工业应用中日益广泛,但因母材理化性能差异,导致焊接难度大。根据金属元素冶金相容性选用Zr-Ni组合结构设计填充金属,并使用超声波焊接方法制备填充材料。研究Zr-Ni中间层对TC4/304SS Nd:YAG(掺钕钇铝石榴石)脉冲激光焊接金属间化合物(IMCs)生长行为与机械性能的影响,确定填充材料的可行性。通过扫描电镜(SEM)、能谱仪(EDS)和X射线衍射(XRD)分析接头微观结构。使用显微硬度仪及抗拉强度测试评价接头力学性能。表明:在最优参数下TC4/304SS接头无宏观裂纹,沿界面均匀分布的IMCs呈现2层颜色明显不同的组织结构,焊缝生成了FeTi,Fe2Ti和少量Ti5Cr7Fe17IMCs,接头在正应力作用下发生脆性解理断裂;制备的Zr-Ni中间层有效阻隔了母材混合,边界形成的固溶体有助于提高接头强度,同时形成的Zr/Ni IMCs具有延展性,TC4/Zr-Ni/304SS接头抗拉强度达213.7 MPa。所制备的填充层对提升该异种金属接头力学性能和分析其焊缝组织变化具有重要意义。     

Preparation and Upconversion Luminescence of Y_3Al_5O_(12):Yb~(3+),Er~(3+)Transparent Ceramics

Crystalline Y3Al5O12(YAG) exists in the cubicform,having a garnet structure[1 ,2],and has excellentchemical stability ,good optical and high temperaturecreep chemical stability[3 ~5]. YAG single crystal hasdrawn considerable attention since the early 1960s ,asit isthei mportant crystal forfluorescent andsolid-statelasers . However ,it is hard to prepare large size sam-ples and dope high concentrationions in YAGcrystal .Conversely ,the fabrication of YAGtransparent ceram-ics is relatively…