化学共沉淀法制备BaMgA110O17:Eu2+荧光粉

以Ba(NO3)2,Mg(NO3)2·6H2O,Al(NO3)3·9H2O,Eu2O3和适量表面活性剂为原料,以NH4HCO3为沉淀剂,采用化学共沉淀法一次煅烧工艺,在1200℃下合成单相BaMgA110O17:Eu2+蓝色荧光粉。结果表明,化学共沉淀法的煅烧温度比传统的高温固相法降低了400℃左右,合成的荧光粉体色白、发光强度高、结构松散且无烧结现象,粒度主要分布在190～295nm之间。在254nm的紫外光激发下,BaMgA110O17:Eu2+的发射光谱最强峰在450nm左右;当Eu2+掺杂浓度为14%时,发光强度最大。     

分散在SiO2中的Y2O3:Eu3+纳米晶的光学性质

采用正硅酸乙酯为SiO2的先驱体,采用Sol-Gel法制备了分散在SiO2基质中的Y2O3Eu3+纳米晶发光材料,研究了材料在不同退火温度下Eu3+稀土离子的光学性质.发射光谱表明随着退火温度的不同,光谱发生了明显变化,并特别地分析了样品在1300℃退火温度下,平均粒径50 nm颗粒样品的发光特性,实验结果表明,在这种发光材料中Eu3+占居4种格位和1种表面态.     

均分散球形Y2O3：Eu^3＋纳米晶的制备

采用凝胶网格共沉淀法，以明胶为反应基质制备了单分散球形纳米Y2O3：Eu^3 荧光粉，考察了制备条件对产物粒径的影响。利用X射线衍射(XRD)、透射电子显微镜(TEM)和荧光光谱等手段对样品进行了表征。结果表明：该法制得产物为球形，一次晶粒粒径在13nm～25am之间，且粒度分布均匀，与微米晶相比，该纳米晶的激发光谱发生明显红移。     

Photoluminescence properties of nanocrystalline Y2O3:Eu3+ in different environments

In this study the optical properties of nanocrystalline europium doped yttria Y₂O₃:Eu³⁺ were investigated in dependence on different environments such as a silica based molecular sieve MCM-41, with a pore sizes of 2.7nm, a free nanopowder on air and in aqueous solution. All these results were compared to a commercial lamp phosphor powder with a grain size of about 5μm. Investigated optical properties are the photoluminescence emission spectra, the excitation spectra, the lifetimes and the quantum efficiencies. Heavy differences of the change transfer process will be reported and discussed with respect to the structure. A low optical quantum efficiency of the nanoparticles is explained by changes in the crystal field.     

CaAl2O4：Eu^2＋，Nd^3＋纳米粉体的合成与表征

采用溶胶一凝胶法制备了CaAl2O4：Eu^2＋，Nd^3＋纳米粉体发光材料。样品的XRD和SEM分析结果表明：800℃已形成CaAl2O4晶相；样品颗粒尺寸随灼烧温度升高而增加，平均粒径约为20nm～40nm。光谱分析表明：样品的激发光谱为240nm～400nm的宽带谱，在256．6nm和330．6nm处有激发峰。发光光谱是386nm～500nm的宽带谱，峰值位于440nm，与CaAl2O4：Eu^2＋，Nd^3＋粗晶材料相比，光谱发生了“蓝移”现象。样品的热释光峰值位于206℃，与粗晶材料相比，峰值向高温移动了96℃，热释发光峰曲线形状也变宽。样品的发光衰减是由初始的快衰减和随后的慢衰减构成，余辉时间为5h。     

沉淀法制备纳米Eu：Y2O3荧光粉

试验分别以微米级Y2O3、Eu2O3粉体为原料，碳酸氢铵为沉淀剂，三乙醇胺为络合剂，采用三乙醇胺络合沉淀法制备了化学组成为NC6H12（NH4）Y2（CO3）（NO3）2·nH2O的前驱体。研究了前驱体在不同的煅烧温度下的物相变化，结果表明，前驱体在500℃保温2h即可直接生成立方相的Eu：Y2O3，在1000℃保温2h的条件下得到了结晶度高、分散性好、平均粒径为50～60nm、近球形的纳米Eu：Y2O3荧光粉。     

Y2O2SO4: Eu3+ 亚微米棒的合成及发光性能

以Na2SO4和K2SO4为熔盐,采用熔盐法合成了一维Y2O2SO4:Eu3+亚微米棒。应用X射线衍射、扫描电子显微镜和光谱仪等方法对合成产物的晶体结构、形貌和发光性能进行表征。考察了烧结温度、Eu3+掺杂浓度对合成产物的晶体结构、形貌和发光性能的影响,结果表明,原料混合物在1100℃空气中煅烧2 h可合成纯相、表面光滑的Y2O2SO4: Eu3+亚微米棒,Y2O2SO4: Eu3+亚微米棒的长边大于10 μm,短边为500~800 nm。在270nm紫外光的激发下,Y2O2SO4: Eu3+亚微米棒呈红光发射,最强发射峰位于616 nm处,归属于Eu3+的5D0→7F2跃迁,Y2O2SO4: Eu3+亚微米棒Eu3+的最佳掺杂浓度为10mol%。     

溶胶-凝胶法制备Ca2MgSi2O7:Eu2 ,Dy3 发光粉

以正硅酸乙酯、硝酸盐等为原料,用溶胶.凝胶法制备了Ca2MgSi2O7Eu2 ,Dy3 长余辉发光粉,探讨了前驱体制备工艺条件,用XRD等手段对发光粉进行了表征.结果表明在pH=1～3,R≥4,控制共溶溶剂的用量,室温下即可形成均匀透明的溶胶和凝胶.前驱体在1100℃烧结3 h制备出Ca2MgSi2O7Eu2 ,Dy3 长余辉发光粉.发光粉具有光致发光行为和长余辉发光特性,其发出的余辉为黄绿色,发光亮度低、余辉时间短,仅1 h左右,其激发光谱在340～480nm之间存在一个强度较低的激发带,发射光谱的发射峰位于528nm.     

均分散球形Y2O3：Eu^3＋纳米晶的制备研究

采用凝胶网格共沉淀法，以明胶为反应基质制备单分散球形纳米Y2O3：Eu^3 荧光粉，考察了制备条件对产物粒径的影响。利用X射线衍射(XRD)、透射电镜(TEM)和荧光光谱等手段对样品进行了表征。结果表明：该法制得产物为球形，一次晶粒粒径在13nm～25nm之间，且粒度分布均匀，与微米晶相比，该纳米晶的激发光谱发生明显红移。     

纳米SrAl2O4:Eu,Dy发光特性及浓度猝灭

用溶胶-凝胶法合成了不同Eu2+掺杂浓度的SrAl2O4Eu2+,Dy3+纳米晶体,探讨了纳米晶体的发光性能及浓度猝灭.结果发现纳米晶体与相应的常规尺寸的发光粉末材料相比,发射光谱和激发光谱的主峰位置均出现了明显的蓝移,发光强度和猝灭浓度有明显的提高,余辉衰减速度加快.认为蓝移现象以及余辉衰减变快,主要归因于发光粉体纳米粒子的量子尺寸效应.     

燃烧法合成SrAl2O4:Eu2+,Nd3+长余辉发光材料的研究

利用相应的金属硝酸盐和尿素发生氧化还原的燃烧反应,在600℃的炉温下,制备了发绿光的SrAl2O4:Eu2 ,Nd3 长余辉材料,该材料属于单斜晶系。研究结果表明,在制备SrAl2O4:Eu2 ,Nd3 时,尿素的加入量与尿素理论的加入量之比为2.0,pH=2时,所制得的发光体的发光强度最大,粒度较小。     

Yb2Ge,Eu2Ge and Eu2Si: new PbCl2-type compounds

The intermetallic compounds Yb₂Ge, Eu₂Ge and Eu₂Si were synthesized from the elements by HF melting in tantalum crucibles. The three phases crystallize in the PbCl₂ structure type, as shown by Rietveld refinement of powder pattern intensity data. The structure of Yb₂Ge was confirmed by a single crystal study.     

Preparation of Y2O3：Eu^3＋ phosphor by molten salt assisted method

A kind of fine and quasi-spherical Y2O3：Eu^3＋ phosphor was prepared by firing a preparative precursor at 1 200 ℃ for 2 h with the molten salts of Na2CO3, S and NaCl. The precursor was obtained by homogeneous precipitation of yttrium and europium with oxalic acid when using EDTA, citric acid or starch as complexant. The structure and morphology of the phosphors were characterized by XRD and SEM, respectively. The influence of complexing environment, firing temperature and molten salts on formation of the phosphor Y2O3：Eu^3＋ was discussed. The result show that the prepared Y2O3：Eu^3＋ phosphor is of quasi-spherical structure with size of 2-3 μm. Its luminescent intensity is 30% higher than that of the same phosphor prepared by the same procedure but without molten salts, and is 5% higher than that of commercial Y2O3：Eu^3＋ red phosphor.     

Preparation of pure nano-grained Si2N2O ceramic

Pure Si₂N₂O ceramic is fabricated by nitridizing a powder mixture of Si and SiO₂. Results show that the prepared Si₂N₂O is composed of nano-particles with a size of about 50 nm. Analysis and discussion are focused on the formation mechanism of the nano-grained Si₂N₂O ceramic based on thermodynamics calculation, micro-morphologies and phase composition analysis. Preferential formation of Si₃N₄ on the surface of nano-SiO₂ particles at below melting point of Si and then successive in-situ transformation of SiO₂ and Si₃N₄ into Si₂N₂O at above melting point of Si are considered as the key reasons to form the pure nano-grained Si₂N₂O ceramic.     

Mechanoluminescent determination of the mode I stress intensity factor in SrAl2O4:Eu2+,Dy3+

The use of mechanoluminescence (ML) has enabled a new technique for the determination of the mode I stress intensity factor (SIF) in SrAl₂O₄:Eu²⁺,Dy³⁺ (SAO). The stress rate fields and its cumulative isostress contour patterns in terms of ML in the vicinity of a crack tip during compact tension were evaluated based on the two different stress criteria of the hydrostatic and deviator in triggering the trap-releasing processes of the ML mechanism. The magnitude and shape of the crack tip stress field predicted by the deviator stress criterion rather than by the hydrostatic stress criterion showed good agreement with the experimental ML evidence in a determination of the SIF from the ML intensity. The analysis derived from the deviator stress criteria not only allowed the possibility of characterizing the fracture toughness in a range of modes under static and dynamic crack propagation, but also provided a better understanding of the ML mechanism of the trap-releasing process in SAO.     

PREPARATION AND CHAIACTERISTICS OF (Y,Gd)2O3:Eu3+ NANOPARTICLES

用湿化学共沉淀法制备了(Y, Gd)2O3:Eu3+纳米粒子. 用XRD, TEM, SEM及差示/热重分析 (DSC/TG)手段对粉体进行了表征. 用荧光光度计分析了样品的激发光谱和发射光谱. 结果表明： 在煅烧温度为800 ℃保温2 h时, 合成出近似球形、粒径均匀且分散性好的(Y, Gd)2O3:Eu3+纳米粒 子, 一次颗粒尺寸约为20 nm. 样品在波长为612.0 nm监控光下激发, 出现235和250 nm两个激发 峰, 分别为(Y, Gd)2O3基质吸收和Eu3+迁移态(CTS)吸收造成的. 两个波长激发下的发射光谱峰强 度前者高于后者. 当掺杂Eu3的摩尔浓度为3%时, 发射光谱对应5D07F2 能级跃迁的相对峰强度 最大, 当Eu3+掺杂的摩尔浓度为7%时, 相对峰强度反而降低, 这是由于Eu3+的浓度猝灭造成的.     

机械力化学合成Y2O3：Eu^3＋纳米材料及其发光性能

采用机械力化学法制备厂纳米Y2O3：Eu^3＋粉体。利用TG-DSC，XRD，TEM等实验技术对其进行了表征，并对其光谱特性进行r研究。结果表明：所得纳米Y2O3：Eu^3＋为球形，粒度分布均匀，粒径为约30nm～50nm，与体材料相比，该纳米品的发射光普发生蓝移，激发光谱发生红移。     

SrAl2O4：Eu^2＋，Dy^3＋材料发光性能的影响因素的研究

采用高温固相法在氢气还原气氛下制备了光致发光材料SrAl2O4：Eu^2＋,Dy^3＋。研究助熔剂用量、焙烧温度、保温时间等因素对材料发光性能的影响。研究表明助熔剂用量、焙烧温度、保温时间对材料的发光性能影响很大,且均存在一个最佳值,当基质原料中助熔剂用量为15％（质量分数）,焙烧温度为1250℃,保温时间为4h时所得发光材料的性能最好。XRD测试表明,所制备的材料SrAl2O4：Eu^2＋,Dy^3＋属单斜晶系;发射光谱测试表明,材料SrAl2O4：Eu^2＋,Dy^3＋的发光光谱是以Eu^2＋为发光中心位于525nm的带状谱。     

溶胶-凝胶法制备Eu掺杂Sr_2MgSi_2O_7光致发光性能

采用溶胶-凝胶(sol-gel)法制备稀土离子Eu掺杂的Sr2MgSi2O7硅酸盐基发光材料,通过X射线衍射仪(XRD)、透射电子显微镜(TEM)、荧光分光光度计(PL)对样品的晶体结构、形貌及光学性能进行测试。XRD测试结果表明,在较低的处理温度下可获得Sr2MgSi2O7,但样品中也存在其它的杂质相。荧光光谱测试结果表明,经空气中处理的Eu3+在395 nm光激发下产生590 nm、610 nm的发射峰,通过氢气还原处理后得到的Eu2+离子的发光从250到400 nm的紫外区可以激发峰值为460 nm左右的宽谱带,且随氢气还原温度的升高和Eu离子掺杂浓度的提高发光强度也增强。