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1.
共沉淀法合成Yb3+∶Y2O3纳米粉及透明陶瓷的性能   总被引:1,自引:0,他引:1  
以Y2O3为基质材料,掺杂不同含量的Yb3+,采用共沉淀法制备出性能良好的Yb3+∶Y2O3纳米粉,将粉体在1 700 ℃和真空度为1×10-3 Pa下烧结5 h得到Yb3+∶Y2O3透明陶瓷。用XRD、TEM、UV-Vis、FL分别对样品的结构、形貌和发光性能进行了研究。结果表明:Yb3+完全固溶于Y2O3的立方晶格中,Yb3+∶Y2O3粉体大小均匀,近似球形,尺寸约40~60 nm。Yb3+∶Y2O3透明陶瓷相对密度为99.7%,在波长600~800 nm范围内其透光率达到80%。Yb3+∶Y2O3透明陶瓷在950 nm处吸收线宽达到26 nm,在1 031 nm和1 076 nm处的发射线宽分别为13 nm和17 nm。  相似文献   

2.
夏文生  张达  翁维正  万惠霖 《催化学报》2013,34(11):2130-2137
采用密度泛函理论方法考察了La-O团簇上超氧物种与过氧物种间转化的连接途径. 单重态下, 团簇上单个超氧物种可通过一系列臭氧物种转化为过氧物种, 且转化能垒较高;三重态下, 单个超氧物种则并无与过氧物种间连接的途径. 然而, La-O团簇上两超氧物种间的相互作用及其转化也具单重态和三重态两条途径. 三重态下, 超氧物种可很容易地转化为过氧物种(O2- + O2-↔O22- + O2), 超氧物种与过氧物种处于快速的交换状态之中;单重态下, 超氧物种转化为过氧物种则需较高的活化能垒, 表明在单重态下这些氧物种具有较高的稳定性.  相似文献   

3.
以B2O3为助熔剂,在1 350 ℃、还原性气氛下成功制备了SrAl2O4单相粉末样品。用同样的方法制备了系列单相Sr1-x-yAl2O4:Eu2+x,Dy3+y·nB2O3(0.005≤x≤0.07, 0.01≤y≤0.05,0.05≤n≤0.25)样品并表征了其长余辉发光特性。结果表明,最佳的Eu2+含量为0.02。辅助激活离子Dy3+在Sr0.98Al2O4:Eu2+0.02中的掺杂在一定范围内可以显著提高亮度和余辉时间,最佳Dy3+含量为0.03。研究不同B2O3含量对Sr0.95Al2O4:Eu2+0.02,Dy3+0.03发光性能的影响,结果说明最佳的B2O3含量为n=0.1,余辉肉眼可见(≥0.32 mcd·m-2)时间达4 000 min。利用正电子湮灭技术和热释光技术,研究和讨论了B2O3对Sr0.95Al2O4:Eu2+0.02,Dy3+0.03的发光和余辉性能的影响,结果表明B2O3的添加有助于Dy3+在晶格中形成深度合适、有益于余辉的空位缺陷。  相似文献   

4.
采用高温固相法制备了2个系列的荧光粉样品:Ba2-xZnGe2O7∶xBi3+(系列Ⅰ)和Ba1.994-yKyZnGe2O7∶0.006Bi3+(系列Ⅱ)。X射线衍射(XRD)测试结果表明,少量Bi3+、K+的掺杂不会明显改变材料的物相结构。样品的荧光光谱测试结果表明,虽然2个系列样品的发光光谱都随组成成分变化有少量变化,但发光颜色基本上均为黄绿色。在358 nm的激发下,荧光粉的发射光谱呈现一个峰值在 500 nm 的宽发射带,归属于 3P11S0能级跃迁。在 500 nm 监测下,荧光粉的最强激发峰位于 358 nm,归属于1S03P1能级跃迁,此外还有一个位于320 nm的肩峰归属于O2--Bi3+电荷转移带。系列Ⅰ样品的光谱数据结果指出,Bi3+的最佳掺杂量x为0.006。在该基质中,Bi3+掺杂取代Ba2+属于不等价取代,会在晶格中产生Ba2+空位或间隙O2-,对材料的发光强度产生负面影响。对此,采用K+与Bi3+协同掺杂起到电荷补偿的作用,填补Ba2+空位或捕获间隙O2-缺陷。空位被填补或间隙被捕获均减少了晶格畸变,从而使发光强度明显提高。系列Ⅱ样品的光谱数据表明,完全电荷补偿的荧光粉样品相比于没有掺K+的样品,其发光强度提高了约2.5倍。  相似文献   

5.
SrAl2O4∶Eu2+,Dy3+纳米长余辉发光材料的制备与表征   总被引:7,自引:0,他引:7  
采用溶胶-凝胶法制备了SrAl2O4∶Eu2+,Dy3+ 纳米长余辉发光材料,研究了pH值、反应温度和络合剂等对溶胶-凝胶形成的影响,研究了灼烧温度对SrAl2O4∶Eu2+,Dy3+ 晶相、颗粒尺度和发光性能的影响。利用XRD, SEM,光谱分析等手段对产物进行了结构和性能分析。实验结果表明,在800 ℃时SrAl2O4晶相开始形成但没有发光,而在1 100 ℃烧结的样品则具有很好的发光性能。样品平均晶粒尺寸随灼烧温度升高而增加,平均晶粒尺寸为20~40 nm。样品的激发光谱是峰值在240,330,378和425 nm的连续宽带谱,发光光谱是峰值在523nm的宽带谱,与SrAl2O4∶Eu2+,Dy3+ 粗晶材料相比,发光光谱发生了“红移”现象。样品的热释光峰值位于157 ℃,与SrAl2O4∶Eu2+,Dy3+ 粗晶材料相比,峰值向低温移动了13℃。  相似文献   

6.
采用水热-均匀共沉淀法制备了纳米SrAl2O4∶Eu2+,Dy3+长余辉发光材料。通过XRD、TEM、荧光光谱、热释光谱对其结构和性能进行分析。XRD结果表明所制备的SrAl2O4∶Eu2+,Dy3+纳米发光材料为单相,属单斜晶系。TEM测试表明纳米SrAl2O4∶Eu2+,Dy3+发光材料为规则的球状粒子,粒径为50~80 nm,且分散性良好。激发和发射光谱测试表明,样品的激发光谱是峰值在356 nm的连续宽带谱,发射光谱是峰值位于512 nm的宽带谱,与SrAl2O4∶Eu2+,Dy3+粗晶材料相比,激发和发射光谱都出现了“蓝移”现象。样品的热释光峰值位于358 K,适合于产生长余辉。  相似文献   

7.
采用高温熔融法制备了Tm3+/Er3+/Ho3+共掺的铋硅酸盐50SiO2-40Bi2O3-5AlF3-5BaF2玻璃。研究了在808 nm激光器(Laser Diode)激发下Tm3+/Er3+/Ho3+共掺的铋硅酸盐在2 060 nm处的发光性能,同时测试及分析了该铋硅酸盐玻璃的差热特性、吸收光谱及荧光光谱。根据吸收光谱以及Judd-Oflet理论,计算了Ho3+的Judd-Oflet强度参数Ωtt=2,4,6)以及Tm3+/Er3+/Ho3+相应的吸收截面。铋硅酸盐玻璃中,Tm2O3、Er2O3和Ho2O3掺杂浓度分别为0.75%、1.0%和0.5%时,2 060 nm处Ho3+5I75I8发射峰强度达到最大。对Tm3+/Er3+/Ho3+ 3种离子的光谱性质和离子间可能存在的能量传递也做了分析。Ho3+在1 953 nm处的最大吸收截面σabs为9.08×10-21 cm2,在2 060 nm处的最大发射截面σem为11.68×10-21 cm2,辐射寿命τmea为2.75 ms,具有良好的增益效应σemτ(3.212×10-20 cm-2·ms)。  相似文献   

8.
采用凝胶-燃烧法制备了稀土Eu3+掺杂的LaMgAl11O19红色荧光粉的前驱粉末, 在低于700℃退火处理时, 得到非晶态样品, 而高于850℃退火处理后为单一六方相结构LaMgAl11O19:Eu3+样品. SEM结果表明, 该法制备的样品为颗粒分布均匀, 粒径在200~400 nm之间的超细粉末. 通过激发光谱和发射光谱研究了Eu3+在LaMgAl11O19基质中的发光性能, 结果显示, 非晶态和晶态La1-xMgAl11O19:x Eu3+样品都可发光, 在613 nm波长光的监测下所得荧光粉的激发光谱为一宽带和系列锐峰, 其最强激发峰出现在蓝光465 nm处, 次强峰为394 nm, 表明该荧光粉与广泛使用的紫外和蓝光LED芯片的输出波长相匹配. 在465 nm波长光的激发下观察到超细LaMgAl11O19粉末中Eu3+的613 nm (5D07F2)强的特征发射, 且随着粉末逐渐成相5D07F2跃迁明显增强, 说明LaMgAl11O19:Eu3+超细粉末可作为白光LED的红色补偿荧光粉.  相似文献   

9.
综合ZnO-Al2O3-SiO2系和锗酸盐玻璃陶瓷的优点,采用熔融-晶化法首次制备了Ho3+/Yb3+共掺以ZnAl2O4为主晶相的ZnO-Al2O3-GeO2-SiO2系玻璃陶瓷。因[GeO4]四面体和[SiO4]四面体都是玻璃网络形成体,讨论了GeO2取代SiO2对玻璃陶瓷样品硬度及发光性能的影响,最终确定GeO2的取代量为10.55%(w/w)时,玻璃陶瓷综合性能最佳。在980 nm泵浦光的激发下,发现强的绿色(546 nm)和弱的红色(650 nm)上转换发光,并研究了不同Ho3+/Yb3+掺杂比对样品上转换发光的影响,最终结果表明当Ho3+/Yb3+掺杂比为1:11(n/n)时样品荧光强度最强,在绿色上转换发光材料方面具有潜在的应用。  相似文献   

10.
采用溶胶凝胶法和浸渍法制备10% Mn/Al2O3-TiO2催化剂,借助TPO、XRD、O2-TPD、Raman、XPS等手段,考察焙烧温度(450~650 ℃)对催化剂结构以及氧化NO性能的影响。TPO结果表明催化剂活性随焙烧温度的升高先增后减,其中焙烧温度为550 ℃时催化剂活性最好。XPS结果显示随着焙烧温度的升高(450~550 ℃),催化剂表面Mn3+的含量逐渐升高,与催化剂活性的强弱成对应关系,并且催化剂晶格氧含量下降,而表面化学吸附氧从40.9%增加到64.8%。Raman分析显示550 ℃焙烧时,催化剂表面存在丰富的Mn2O3活性物种,并且O2-TPD分析也表明随着焙烧温度的升高,晶格氧向表面化学吸附氧流动,提高了化学吸附态氧物种的含量。这些结果表明Mn2O3可能是NO氧化起主要作用的活性Mn物种,释放更多的表面化学吸附氧物种,将有助于促进NO的催化氧化。  相似文献   

11.
Host lattice Ba3Si5O13−δNδ oxonitridosilicates have been synthesized by the traditional solid state reaction method. The lattice structure is based on layers of vertex-linked SiO4 tetrahedrons and Ba2+ ions, where each Ba2+ ion is coordinated by eight oxygen atoms forming distorted square antiprisms. Under an excitation wavelength of 365 nm, Ba3Si5O13−δNδ:Eu2+ and Ba3Si5O13−δNδ:Eu2+,Ce3+ show broad emission bands from about 400-620 nm, with maxima at about 480 nm and half-peak width of around 130 nm. The emission intensity is strongly enhanced by co-doping Ce3+ ions into the Ba3Si5O13−δNδ:Eu2+ phosphor, which could be explained by energy transfer. The excitation band from the near UV to the blue light region confirms the possibility that Ba3Si5O13−δNδ:Eu2+, Ce3+ could be used as a phosphor for white LEDs.  相似文献   

12.
The LiInW2O8:Eu3+, LiInW2O8:Dy3+ and LiInW2O8:Eu3+/Dy3+ phosphors were synthesized by solid-state reaction and their photoluminescence properties were studied. Under UV excitation, the LiInW2O8:Eu3+ phosphor exhibits an intense red emission whereas the LiInW2O8:Dy3+ and LiInW2O8:Dy3+/Eu3+ phosphors show a white emission. The WO6 octahedra play a major role in the luminescence of the host lattice, characterized by a blue emission under UV excitation. The emission of activator ion results from an efficient energy transfer from the LiInW2O8 host lattice to the Eu3+ and Dy3+ ions. The LiIn0.97Dy3+0.03W2O8 and LiIn0.965 Dy3+0.03Eu3+0.005W2O8 samples, optimized for white emission, are interesting candidates for solid-state lighting applications.  相似文献   

13.
Spectral-luminescent characteristics of Sr2Y8(SiO4)6O2: Eu powder crystal phosphor with the apatite structure and high-intensity luminescence of Eu3+ ions have been studied. The charge state of europium in the samples has been characterized by means of X-ray L3-adsorption spectroscopy. It was established that Eu3+ forms two types of optical centers. Besides, luminescence of Eu2+ions was found. Reduction Eu3+→Eu2+ was considered, which may be due to vacancy formation in the 4f crystal lattice position and to negative charge transfer by this vacancy to two ions. Thus, in the silicate lattice there exist inhomogeneously distributed oxygen-deficient centers, which are responsible for nonradiative transfer of excitation energy to Eu3+ and Eu2+ ions. To study electron-vibrational interactions in the crystal phosphor samples, their IR and Raman spectra were examined. In the luminescence spectrum of Eu2+, a series of low-intensity bands caused by interaction of the 4f65d state of Eu2+ with silicate lattice vibrations was observed.  相似文献   

14.
In ground mixtures of In2O3 and NH4Y, incorporation of In+ cations into the zeolitic phase occurs upon thermal treatment by partial reductive solid-state ion exchange associated with oxidation of ammonium ions or released ammonia to N2 and NH2OH. Cationic InO+ species, created in zeolites by reductive solid-state ion exchange of In2O3/NH4-zeolite mixtures in hydrogen atmosphere and subsequent oxidation of the In+ lattice cations by oxygen, do not undergo autoreduction up to 970 K. Reductive solid-state ion exchange easily proceeds in carbon monoxide atmosphere at temperatures between 620 and 770 K. The significance of these observations for the use of indium-containing zeolites as catalysts is discussed.  相似文献   

15.
By activation of the new host lattice Sr3La2W2O12 with the trivalent rare earth ions Nd, Eu, Ho, Er, Tm, Yb an intense emission in the visible and/or infrared region is obtained. Energy transfer from Er3+ to Tm3+ and Nd3+ to Yb3+ has been found to occur. The excitation, emission, and diffuse reflectance spectra are analyzed for Sr3La2W2O12: Ln3+ (Ln = Nd, Sm, Eu, Dy, Ho, Er, Tm, Yb).  相似文献   

16.
Undoped and RE ions doped SrB2Si2O8 were successfully synthesized. After the application of UV and VUV spectroscopy measurements, we made a novel discovery that the emission of SrB2Si2O8:Eu prepared in air can be switched between red and blue by the different excitations. The information is that quite a part of Eu3+ was spontaneously reduced to Eu2+ in air. The PL properties of Eu2+ in VUV and Eu3+, Ce3+ and Tb3+ in UV-VUV region in SrB2Si2O8 were evaluated for the first time. The excitation mechanisms of the O2−-Eu3+ CT, Ce3+f-d and Tb3+f-d transitions in UV region as well as the Eu3+f-d, O2−-Ce3+ CT, O2−-Tb3+ CT transitions and the host lattice absorption in VUV region were established. In addition, first principles calculation within the LDA of the DFT was applied to calculate the electronic structure and linear optical properties of SrB2Si2O8 and the results were compared with the experimental data.  相似文献   

17.
Two pure light rare earth iron garnets Pr3Fe5O12 and Nd3Fe5O12 single crystals were synthesized under mild hydrothermal conditions and structurally characterized by single crystal and powder X-ray diffraction methods. Both compounds crystallize in cubic space group Ia3?d with lattice parameters a=12.670(2) Å for Pr3Fe5O12 and a=12.633(2) Å for Nd3Fe5O12, respectively. The synthesis of compounds was studied with regard to phase evolution and morphology development with hydrothermal conditions. We proposed the formation mechanisms and formulated a reasonable explanation for their growth habits. Ferrimagnetic Curie temperatures which have been inferred from thermo-magnetization curves were 580 K for Pr3Fe5O12 and 565 K for Nd3Fe5O12, and the transitions of long range order were also evidenced by differential scanning calorimetry method. The result of magnetic properties has shown that moments of the large radius Pr3+ and Nd3+ ions are parallelly coupled with net moments of iron ions.  相似文献   

18.
Dissociation of molecular hydrogen (H2) is extensively studied to understand the mechanism of hydrogenation reactions. In this study, H2 dissociation by Au1-doped closed-shell titanium oxide cluster anions AuTi3O7- and AuTi3O8- has been identified by mass spectrometry and quantum chemistry calculations. The clusters were generated by laser ablation and massselected to react with H2 in an ion trap reactor. In the reaction of AuTi3O8- with H2, the ion pair Au+-O22- rather than Au+-O2- is the active site to promote H2 dissociation. This finding is in contrast with the previous result that the lattice oxygen is usually the reactive oxygen species in H2 dissociation. The higher reactivity of the peroxide species is further supported by frontier molecular orbital analysis. This study provides new insights into gold catalysis involving H2 activation and dissociation.  相似文献   

19.
An increased solubility of Nd3+ in YAG has been achieved by means of expansion of its crystal lattice with Sc3+ ions substituting for Al3+ ions in the octahedral sites. A number of other scandium substituted rare earth aluminum garnets of general formula {R3}[Sc2](Al3)O12 have been prepared and results are compared with similar compounds in {R3}[Sc2](Fe3)O12 systems. It is shown that the expansion of the YAG lattice by octahedral substitution significantly increases the solubility of Nd3+ on dodecahedral sites. The results of substitution of Sc in other rare earth-aluminum systems appear to be consistent with results obtained in the yttrium-aluminum system and so ions bigger than Gd3+, such as Eu3+ and Sm3+, can form garnets {Eu3}[Sc2](Al3)O12 and {Sm3}[Sc2](Al3)O12.  相似文献   

20.
Barium calcium magnesium silicate (BaCa2MgSi2O8), a compound whose space group was obtained via X-ray diffraction data, was re-investigated using neutron diffraction techniques. A combined powder X-ray and neutron Rietveld method revealed that BaCa2MgSi2O8 crystallizes in the trigonal space group P3? (Z=1, a=5.42708(5) Å, c=6.79455(7) Å, V=173.310(4) Å3; Rp/Rwp=5.52%/7.63%), instead of the previously believed space group P3?m1. The difference in the two structures arises from the displacement of the O2 atom. Blue emission from Ba0.98Eu0.02Ca2MgSi2O8 under 325-nm excitation is ascribed to the 4f65d1→4f7 transitions of Eu2+ ions at Ba sites and Ca sites. Site assignment of Eu2+ ions in the titled compound was performed by analysis of emission spectra at temperatures in the range of 4.2-300 K.  相似文献   

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