溶胶凝胶法制备的Y3Al5O12：Tb^3＋,Ce^3＋的光学性能及能量传递研究

用溶胶凝胶法制备了一系列不同掺杂浓度的Y3Al5O12（YAG）：Tb3＋,Ce3＋荧光粉,对其物相、光学性能和能量传递进行了研究。多晶粉末X-射线衍射结果表明,所有样品均为YAG晶相,没有其它杂相。当样品在Tb3＋的特征激发峰273 nm激发时,除了Tb3＋的特征发射外,还观察到位于467 nm的YAG基质的电荷迁移带、位于520 nm的Ce3＋的2D3/2,5/2→2F5/2,7/2跃迁,这说明可能存在Tb3＋到Ce3＋的单向非辐射能量传递。通过监测共掺样品520 nm的发光,得到273 nm的激发峰,使得Tb3＋（5D3）到Ce3＋（2Di,i=5/2,3/2）的单向非辐射能量传递得到验证;并且随着掺杂Tb3＋浓度的增大,273 nm激发峰增强。同时,Ce3＋掺杂YAG：Tb3＋并没有使Tb3＋发光增强,相反YAG：Tb3＋,Ce3＋中Tb3＋发光与YAG：Tb3＋相比有1个数量级的减弱,造成这种情况的可能原因,一是Tb3＋到Ce3＋的单向非辐射能量传递,使得Tb3＋发光减弱;二是Ce3＋掺杂YAG：Tb3＋后基质所多吸收的能量传给了Ce3＋而非Tb3＋。     

新型GdAlO3：RE荧光粉多元掺杂及发光机制研究

采用柠檬酸盐硝酸盐燃烧法制备GaAlO3：RE荧光粉体．在紫外光激发T(254m)发现Pr共掺杂对GaAlO3：Eu红色荧光粉体发光有降低作用；Ce共掺杂对GaAlO3：Tb绿色荧光粉体发光有降低作用．激发谱研究表明，共掺杂时分别存在Eu→Pr、Tb→Ce的声子支持的共振能量传递，造成GaAlO3：Eu、GaAlO3：Tb荧光粉体发光强度降低．     

Dy3+和Tb3+掺杂硅酸盐玻璃的发光性能

用高温熔融法分别制备了Tb3 抖和Dy3 单掺和共掺的硅酸盐发光玻璃,并分析了其光谱性质.根据Dy3 和Tb3 掺杂硅酸盐玻璃的激发和发射光谱、发光衰减时间谱等特性,研究了Dy3 与Tb3 之间的能量传递关系.结果表明:在硅酸盐玻璃中,Dy3 能敏化Tb3 的特征发光,其能量传递方式为非辐射共振传递.Dy3 和Tb3 共掺的硅酸盐玻璃的发光性能明显提高,1%(质量分数,下同)D广的掺入可使7%Tb3 掺杂的硅酸盐玻璃中Tb3 的550nm特征发光强度增加55%～60%.     

绿色荧光粉Ca_9Al(PO_4)_7:Tb~(3+),Ce~(3+)的发光特性

采用固相法合成Ca9Al(PO4)7:Tb3+,Ce3+绿色荧光粉,研究了材料的发光性质。结果表明,以377 nm近紫外光作为激发源时,Ca9Al(PO4)7:Tb3+呈现出多峰特征,主峰位于491、545、589和623 nm,分别对应Tb3+的5D4→7F6,5D4→7F5,5D4→7F4和5D4→7F3跃迁发射,其中545 nm发射峰最强,从而材料整体发射绿光;监测545 nm发射峰,对应的激发光谱为多峰特征,覆盖300~390 nm;增大Tb3+的掺杂量,发现Ca9Al(PO4)7:Tb3+的发射强度逐渐增大,在实验范围内,并未出现浓度猝灭现象;通过添加A+(A=Li、Na和K)以及敏化剂Ce3+,有效增强了Tb3+在Ca9Al(PO4)7中的发射强度。测量了不同Tb3+掺杂量下材料的色坐标,发现Ca9Al(PO4)7:Tb3+的色坐标基本不变,位于绿色区域。     

Eu3+,Ce3+共掺硼硅酸锌玻璃的发光性能及能量传递

采用高温液相法制备了50ZnO-30SiO2-20B2O3∶Eu3+,Ce3+玻璃。测试了样品的激发光谱和发射光谱。结果表明:在紫外光激发下,该玻璃可以发出明亮的红色光。其中580 nm,593 nm,617 nm,655 nm和706 nm波长处的发射峰分别对应于Eu3+的5D0→7F0,5D0→7F1,5D0→7F2,5D0→7F3和5D0→7F4跃迁发射,其中5D0→7F2跃迁发射强度最大,同时发现在450 nm处存在Ce3+的5D→2FJ(J=7/2,5/2)特征发射峰。首次发现在该发光玻璃50ZnO-30SiO2-20B2O3∶Eu3+,Ce3+中存在着Ce3+→Eu3+能量传递现象,其中Ce3+起敏化作用。     

Y_2SiO_5∶Ce~(3+),Tb~(3+)发光性能及Ce,Tb间的能量传递研究

采用液相沉淀法合成Y_2SiO_5∶Ce~(~(3+)),Tb~(~(3+))发光材料。采用X射线粉末衍射仪(XRD)、扫描电镜(SEM)、荧光分光光度计以及国际照明委员会(CIE)色度坐标图对其相的组成、光谱学和发光特性进行了研究。Y2Si O5∶Tb~(3+)激发光谱中存在较强的基质激发峰,在发射光谱中,发现Tb~(3+)的5D4→7FJ(J=6,5,4,3)跃迁,最大发射中心位于545nm(5D4→7F5跃迁)。在Y_2SiO_5∶Ce~(~(3+)),Tb~(~(3+))双掺体系中,Tb~(3+)的发光强度随Ce~(3+)的浓度增加而增强,存在Ce~(3+)→Tb~(3+)能量传递,尤其是Tb~(3+)的5D4→7F5跃迁发射显著增强,有望成为一种有发展前途的绿色荧光材料。     

Ca3MgSi2O8:RE(RE=Eu2+,Ce3+,Tb3+)的发光性能

采用高温固相法在还原气氛下合成了Ca3MgSi2O8:RE(RE=Eu2 ,Ce3 ,Tb3 )系列样品.用荧光光谱仪研究了样品掺杂Eu2 ,Ce3 ,Tb3 后的光谱性质.样品Ca3MgSi2O8:Ce3 在紫外光激发下呈蓝紫色发射;样品Ca3MgSi2O8:Eu2 在紫外光激发下则呈绿色发射.分别讨论了Ce3 ,Eu2 和Ce3 ,Tb3 共激活焦硅酸钙盐在紫外光激发下的光谱特性和其中存在的能量传递机理,发现Ce3 分别对Eu2 和Tb3 有敏化作用.     

Tb~(3+)在Lu_3Ga_5O_(12)中的光致发光性质及浓度猝灭机制

采用高温固相合成法在还原气氛中制备了(Lu1–xTbx)3Ga5O12荧光粉,研究了其晶体结构、光致发光性能以及Tb3+掺杂浓度对荧光粉性能的影响规律与机制。研究表明:荧光粉具有石榴石型晶体结构,当x增加时,晶格膨胀。荧光粉的激发光谱由归属于Tb3+的4f 8→4f 7 5d1跃迁的A、B两个宽激发带以及归属于4f 8→4f 8跃迁的一些窄谱峰构成;随x的增加,A、B带发生红移,带间距缩小。在紫外光激发下,荧光粉发射绿光;发射光谱对应于Tb3+的5D4→7FJ和5D3→7FJ跃迁,其中5D4→7F5跃迁发射最强。5D4→7FJ各跃迁发射的浓度猝灭以交互作用为主,猝灭浓度xm=0.08。与5D4→7FJ跃迁相比,5D3→7FJ猝灭浓度低,猝灭机制以电偶极–电偶极相互作用下交叉弛豫为主。     

Ba3Tb(BO3)3:Eu3+的制备与发光性质

采用高温固相法合成了Ba3Tb(BO3)3:Eu3+红色荧光粉,并研究了Ba3Tb(BO3)3:Eu3+的发光特性。Ba3Tb(BO3)3:Eu3+的激发光谱包含250nm～330nm和350nm～400nm的2个宽带,最大峰值位于383nm,可以被紫外-近紫外发光二极管(light-emitting diodes,LED)有效激发。Ba3Tb(BO3)3:Eu3+的发射谱显示出4组发射峰,其主发射峰位于620nm,对应Eu3+的5D0→7F2跃迁;Eu3+掺杂摩尔分数为2%时,Ba3Tb(BO3)3:Eu3+发光亮度最高。经分析发现Ba3Tb(BO3)3:Eu3+存在Tb3+→Eu3+的能量传递。     

Tb~(3+)、Gd~(3+)对硅酸盐发光玻璃发光性能的影响

对Nb3 + 激活的硅酸盐发光玻璃进行了研究 ,讨论了Tb3+ 和Gd3 + 对玻璃发光性能的影响。结果表明 :Tb3+ 激活的硅酸盐玻璃在紫外线和X 射线的激发下 ,产生蓝色荧光和较强的绿色荧光 ;随着Tb3+ 离子浓度的增加 ,Tb3 + 离子5D3 能级的能量向5D4 能级转移 ,绿色荧光得到增强 ;Gd3 + 离子通过无辐射能量共振方式对Tb3+ 离子的发光起到了敏化作用 ,加入Gd3+ 进一步提高了Tb3+ 激活硅酸盐玻璃的发光强度     

Structural,magnetic and magnetocaloric properties of the rare earth (RE) molybdate RE2MoO6 (RE = Dy,Tb and Gd) oxides

Reported here is a systematical investigation on the crystal structure, magnetic properties and magnetocaloric (MC) effect of three rare earth (RE) molybdate RE₂MoO₆ (RE = Dy, Tb and Gd) oxides. The X-ray powder diffraction and the morphology as examined using the scanning electron microscope indicate phase-pure and polycrystalline nature of these oxides. The temperature (2–100 K) and magnetic field (up to 5 T) dependence of the magnetic measurements determine the magnetic phase transition (MPT) and MC properties. All the present RE₂MoO₆ oxides crystallize in a monoclinic structure belonging to C2/c space group with the antiferromagnetic ordering at low temperature. Moreover, the RE₂MoO₆ oxides hold reasonable values of MC parameters including the maximum isothermal magnetic entropy change/temperature-averaged entropy change (2 K lift) and relative cooling power values have been evaluated with the magnetic change of 0–5 T, yielding 17.22 (17.08) J/kgK and 277.67 J/kg for Dy₂MoO₆, 17.03 (16.83) J/kgK and 261.12 J/kg for Tb₂MoO₆, as well as 27.68 (26.69) J/kgK and 228.14 J/kg for Gd₂MoO₆, respectively. These acceptable MC parameters make the present RE₂MoO₆ oxides potential candidates for cryogenic magnetic refrigeration (MR).     

Enhanced emission of ultra-small-sized LaF(3):RE(3+) (RE = Eu, Tb) nanoparticles through 1,2,4,5-benzenetetracarboxylic acid sensitization

Uniform, ultra-small-sized and well-water-dispersible LaF(3) nanoparticles doped with trivalent rare earth (RE) ions (Eu(3+) or Tb(3+)) have been synthesized by a simple, low temperature synthesis route. The nanoparticles, with sizes of about 3.2 nm (for those doped with Eu(3+)) and 3.0 nm (for those doped with Tb(3+)), are roughly spherical and monodisperse. 1,2,4,5-Benzenetetracarboxylic acid (labeled as BA) as sensitizer has been bonded to the surface of the nanoparticles, which can sensitize the emission of RE(3+) in the LaF(3) nanoparticles. The BA-LaF(3):RE(3+) (RE = Eu or Tb) nanoparticles have a broad absorption band in the UV domain, and show enhanced luminescence of RE(3+) based on an energy transfer from BA ligands to RE(3+) ions (i.e. the so-called "antenna effect"). Due to the dual protection of organic ligands (BA) and inorganic matrices (LaF(3)), BA-LaF(3):RE(3+) (RE = Eu or Tb) nanoparticles have longer excited state lifetimes than LaF(3):RE(3+) (RE = Eu or Tb) nanoparticles as well as lanthanide coordination polymers of BA.     

稀土生物有效性的研究进展

随着稀土在工农业的应用日渐扩展,稀土也广泛进入了生态环境,并且由食物链等渠道进入体内,因此稀土对环境、生态和人体健康的影响,以及对稀土近期和远期生物学效应的研究也越来越引起人们的关注,我国一些科研院所从不同角度探讨了稀土的某些生物学效应,为我国稀土元素的安全性评价提供基础数据。而且应当充分发挥我们这个稀土大国的优势,充分利用我们的稀土资源,进一步研究稀土的有益效应,使科研成果转化为生产力,为促进人类健康,繁荣市场经济,开辟稀土应用的新领域。     

Enhancement of fluorescence and magnetic properties of CeF3:RE3+ (Tb,Gd) nanoparticles via multi-band UV excitation and Li doping regulation

In this study, hydrothermal synthesis of CeF₃: Tb, Gd nanoparticles doped with Li⁺ alkali metal ions were demonstrated using introduction of Li⁺ ions through LiNO₃ nitrate. These nanoparticles have dual properties of magnetic fluorescence. X-ray diffraction, Fourier transform infrared spectrometer, XPS and photoluminescence spectra, and vibrating sample magnetometry were used to characterize structural properties, surface functional groups, fluorescence, and magnetic properties of these particles. Results show that CeF₃: Tb, Gd nanoparticles exhibit bright green light emission under excitation at 258 nm and 378 nm ultraviolet band. Through the modification of Li⁺ ions, luminous intensity of green light is further improved. Energy transfer between rare earth ions was investigated via photoluminescence spectroscopy. This work demonstrates potential applications of Li doped CeF₃: Tb, Gd nanoparticles as photomagnetic dual-functional materials in fields of biological imaging, solid state lighting, and magnetic biological separation.     

Upconverting YbPO4:RE monospheres (RE=Ho,Er, Tm)

Uniform spheres of (Yb_0.98RE_0.02)PO₄ orthophosphate (RE=Ho, Er, and Tm, respectively) were synthesized via a homogeneous precipitation procedure mediated by SO₄^2? anions. The as‐precipitated and 1100°C calcined products were determined via laser‐diffraction particle sizing to have the average diameters of ~2.04 ± 0.67 and 1.80 ± 0.93 μm, respectively. The upconversion luminescence of RE³⁺ under sensitization by the host Yb³⁺ was studied for the calcination products under 978 nm laser excitation, and it was found that the emissions are dominated by a red band at ~650 nm for Ho³⁺ (⁵F₅ → ⁵I₈ transition), similarly strong green (~515‐565 nm, ²H_11/2/⁴S_3/2 → ⁴I_15/2 transition) and red (~640‐680 nm, ⁴F_9/2 → ⁴I_15/2 transition) bands for Er³⁺, and a near‐infrared band at ~800 nm for Tm³⁺ (³H₄ → ³H₆ transition). The number of laser photons needed to populate the emitting state was determined by varying the excitation power, and the possible photon reactions leading to the observed upconversion were discussed.     

RE170、RE170/R227ea与矿物油的互溶性评价

随着制冷剂R22逐步淘汰, RE170、RE170/R227ea新型环保制冷剂有应用前景, 其和润滑油能否互溶直接影响制冷系统的使用效果。根据标准SH/T 0699-2000建立了一套制冷剂和润滑油的互溶性测试系统, 对RE170、RE170/R227ea和矿物油的互溶性进行了试验研究。结果表明:RE170的矿物油溶液在含油率为10%~60%时, 当温度低至-50℃时没有出现分层或絮状物, 二者互溶性非常好;混合制冷剂RE170/R227ea的矿物油溶液在含油率为14.6%±0.5%的基准情况下, 当R227ea的质量分数在35%~60%变动时RE170/R227ea和矿物油的低温两相分离温度随R227ea含量增加而上升, 当R227ea质量分数低于38%时混合制冷剂和矿物油在-50℃时仍能良好互溶, 当R227ea质量分数超过55%时混合制冷剂和矿物油在室温下已经不能互溶。最后, 结合经验公式法和溶解度参数法提出了新的评价方法来评价纯制冷剂及二元混合制冷剂和矿物油的互溶性。     

Self-Propagating High-Temperature Synthesis of α-SiAlON Doped by RE (RE=Eu,Pr,Ce) and Codoped by RE and Yttrium

Self-propagating high-temperature synthesis (SHS) was applied to synthesize α-SiAlON powders doped by RE (RE = Eu,Pr,Ce) and codoped by RE and yttrium. The results showed that the weight ratio of α-SiAlON to (α-SiAlON +β-SiAlON) decreased from 70%, 55%, and 25% for europium-, praseodymium-, and cerium-doped α-SiAlON compositions, respectively, and the weight percentage of α-SiAlON phase increased to 100% for both (Eu,Y) and (Pr,Y) systems and 94% for the (Ce,Y) system, indicating SHS is a promising approach for synthesizing α-SiAlONs stabilized by the cations that could not be incorporated into the α-SiAlON structure by conventional sintering methods.