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纳米Sr2MgSi2O7:Eu2+,Dy3+的长余辉发光行为 总被引:2,自引:0,他引:2
使用溶胶-凝胶技术合成纳米尺度的Sr2MgSi2O7Eu2+,Dy3+长余辉发光材料,比较了该方法与固相法获得的长余辉粉体的光致发光行为和长余辉性能.溶胶-凝胶获得的纯相Sr2MgSi2O7Eu2+,Dy3+长余辉粉体是由纳米尺度的微晶形成的团聚颗粒,具有光致发光行为和长余辉发光特性.其发射峰位于465nm.而固相合成的粉体具有两个发射峰,分别位于404nm和459nm.产生这些差别的原因在于Eu2+在基质晶格中的不同配位情况.固相合成的粉体的余辉发光性能高于溶胶-凝胶粉体,其原因在于高温固相合成在基质内部产生了更高浓度的电子陷阱. 相似文献
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纳米Sr2MgSi2O7:Eu2+,Dy3+的长余辉发光行为 总被引:20,自引:0,他引:20
使用溶胶-凝胶技术合成纳米尺度的Sr2MgSi2O7:Eu^2 ,Dy^3 长余辉发光材料,比较了该方法与固相法获得的长余辉粉体的光致发光行为和长余辉性能.溶胶.凝胶获得的纯相Sr2MgSi2O7:Eu^2 ,Dy^3 长余辉粉体是由纳米尺度的微晶形成的团聚颗粒,具有光致发光行为和长余辉发光特性.其发射峰位于465nm.而固相合成的粉体具有两个发射峰,分别位于404nm和459nm.产生这些差别的原因在于Eu^2 抖在基质品格中的不同配位情况.固相合成的粉体的余辉发光性能高于溶胶-凝胶粉体,其原因在于高温固相合成在基质内部产生了更高浓度的电子陷阱. 相似文献
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蓝色长余辉发光材料Sr2MgSi2O7:Eu2+,Ln3+的合成和性质 总被引:1,自引:0,他引:1
采用凝胶-燃烧法合成了系列稀土掺杂的Sr2MgSi2O7:Eu2 0.02,Ln3 0.04(Ln=La,Ce,Nd,Sm,Gd,Tb,Dy,Ho,Er,Tm)蓝色长余辉发光材料,用X射线粉末衍射(XRD)、扫描电镜(SEM)、荧光分光光度计等对合成产物进行了分析和表征.结果表明:掺杂了不同稀土离子的Sr2MgSi2O7:Eu2 ,Ln3 的晶体结构均为四方晶系结构;其激发、发射光谱的峰形、峰位基本无变化,激发光谱为一宽带,最大激发峰位于402nm处,次激发峰位于415nm处,与高温固相法制得的样品相比,激发峰发生了明显的红移;发射光谱也为一宽带,最大发射峰位于468nm附近,是由典型的Eu2 的4f5d-4f跃迁导致的,不同之处在于其激发光谱、发射光谱强度与余辉性质有所差别,其中Dy3 是最理想的共掺杂稀土离子,Sr2MgSi2O7:Eu2 ,Dy3 的亮度最高、余辉时间最长,可达5h以上;而Sr2MgSi2O7:Eu2 ,Sm3 的发光强度最低,余辉时间最短. 相似文献
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以Ag、Sb、Te单质粉体为原料,采用机械合金化工艺制备了单相的AgSbTe2化合物粉体。系统研究了机械合金化工艺制度,包括球料比、转速、球磨时间对粉体相组成、颗粒尺寸的影响。结果表明,在球料比为20∶1、转速大于400rpm、球磨时间大于15h时,可得到单相AgSbTe2化合物粉体;当球料比为20∶1、转速为600rpm、球磨48h后,可得到平均粒径约370nm单相AgSbTe2化合物粉体,其表面小颗粒尺寸约为50~100nm。 相似文献
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以膨胀石墨和α-Al2O3微粉为原料,采用高能球磨制备了纳米碳包覆的α-Al2O3复合粉体,研究了高能球磨时间和球磨速率对复合粉体物相及形貌的影响。采用X射线衍射仪、场发射扫描电子显微镜和透射电子显微镜对复合粉体的物相、形貌和微观结构进行了表征。结果表明:按膨胀石墨与α-Al2O3质量百分比为1:2,球磨速率为600 r/min,球磨5 h可得到被粒度为20~50 nm碳颗粒包覆的α-Al2O3复合粉体;随着球磨时间延长,石墨(002)晶面特征峰逐渐消失,膨胀石墨中纳米片层会随球磨时间延长不断剥离脱落,并逐渐龟裂成纳米碳颗粒;相同球磨时间下,提高球磨速率可以促进纳米碳颗粒形成,但超过一定速率后纳米碳颗粒粒度不再减少;480 r/min速率球磨5 h未形成纳米碳颗粒包覆复合粉体,600和700 r/min速率球磨5 h后复合粉体形貌基本一致。 相似文献
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使用固相合成技术制备了一系列Gd2O2S长余辉红色发光材料.在243nm紫外光激发下,具有很好的长余辉特性.这些发光材料具有多个发射峰,橙红色余辉发光是这些发射峰共同作用的结果.长余辉的形成是共激发离子Mg2+,Ti4+在Gd2O2S基质中形成一定浓度的电子陷阱的结果.在掺杂离子中,Ti4+的掺杂优于Mg2+的掺杂,而二者的共同掺杂获得了余辉特性更好的橙红色长余辉发光材料. 相似文献
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采用Gd2O3、Dy2O3、H2SO4和NaOH为实验原料,通过共沉淀法合成了Gd2O2SO4∶Dy3+纳米粉体。利用X射线衍射(XRD)、透射电子显微镜(TEM)和光致发光(PL)光谱等手段对合成的粉体进行了表征。XRD分析表明前躯体在空气气氛下900℃煅烧2h能转化成纯相的Gd2O2SO4∶Dy3+。TEM观察显示Gd2O2SO4∶Dy3+粉体形貌为近球形,分散性良好,粒度大小为20~40nm。PL光谱分析表明在277nm紫外光激发下,Gd2O2SO4∶Dy3+的主次发射峰分别位于575nm(黄光)和485nm(蓝光),分别归属于Dy3+的4F9/2→6H13/2和4F9/2→6H15/2跃迁。Dy3+的猝灭浓度是2%(摩尔分数),猝灭机理是由于Dy3+和Dy3+之间的交换相互作用。余辉光谱研究表明Dy3+的4F9/2→6H13/2和4F9/2→6H15/2跃迁均具有e单指数衰减行为,荧光寿命分别为0.468和0.462ms。 相似文献
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Knowledge about vapour-liquid (VLE) is required as a basis of reliable calculations for separation processes. Correlations available for the prediction of T, p, x, y data are less accurate for mixtures at high pressures and mixtures containing supercritical components. The results of VLE experiments are reported and compared with data calculated with equations of state. 相似文献
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We prepared weakly agglomerated powders of ZrO2-CeO2 and HfO2-CeO2 solid solutions 5–8 nm in particle size, consisting of monoclinic and tetragonal phases. After heat treatment at 1200°C, the crystallite size was 30 and 14 nm, respectively. We also examined the effect of precipitate freeze drying on the crystallization of hafnia-based solid solutions containing up to 20 mol % CeO2. 相似文献
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Thermal diffusion coefficients were measured in two gaseous mixtures, in which one component was close to the critical temperature, in the pressure range (19.6–127.4)·104 N/m2 and at a freon concentration of 0.25–0.8. 相似文献
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C. Bersier E. P. Stoll P. F. Meier T. A. Claxton 《Journal of Superconductivity and Novel Magnetism》2002,15(5):399-402
First-principles cluster calculations are reported of the local electronic structure of the three compounds: La2CuO4, Sr2CuO2Cl2, and Sr2CuO2F2. The copper ${\text{3d}}_{x^2 - y^2 } $ and the planar oxygen 2p σ atomic orbitals exhibit a similar degree of covalency. The out-of-plane orbitals, however, are quite different with the ${\text{3}}d_{3z^2 - r^2 } $ atomic orbital lowered significantly in energy for chlorine and fluorine apical positions. 相似文献
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A series of GRIN glass rods have been developed in Li2O-Na2O-Al2O3-TiO2-SiO2 systems. Negative radial refractive index profiles were generated by exchanging Na+ for Li+ ions in these glass rods. It has been observed that TiO2 plays a vital role in increase in the profile depth and maximum change in the refractive index because of its ambivalent nature. Change in the refractive index can be further increased by increasing the concentration of exchanging cation in the base glass. 相似文献
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I. R. Shein S. L. Skornyakov V. I. Anisimov A. L. Ivanovskii 《Journal of Superconductivity and Novel Magnetism》2014,27(1):155-161
The first-principles calculations were performed to predict the elastic and electronic properties of the superconducting ThCr2Si2-type phases CaPd2As2 and SrPd2As2 in comparison with the non-superconducting CeMg2Si2-type phase BaPd2As2. Besides, the same properties were compared for CeMg2Si2- and ThCr2Si2-type polymorphs of BaPd2As2. We found that all these phases are mechanically stable and belong to soft materials with low hardness. The near-Fermi region is formed by the valence states of the blocks [Pd2As2] with decisive contributions of Pd 4d states. The values of N(E F) increase in the sequence: CaPd2As2 < SrPd2As2 < BaPd2As2, i.e. in the reverse sequence relative to the transition temperatures T C. Thus, the change in T C cannot be explained by the electronic factor, i.e. by the simple correlation T C~N(E F). Most likely the decrease in T C in the sequence CaPd2As2 → SrPd2As2 and the absence of a superconducting transition in BaPd2As2 are related to the structural factors and the peculiarities of the electron–phonon coupling mechanism. 相似文献
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本文给出了 Si_2N_2O-Al_2O_3-La_2O_3和 Si_2N_2O-Al_2O_3-CaO 系统的亚固相图。实验结果表明:在 Si_2N_2O-Al_2O_3-CaO 系统中有一个未知结构的新化合物 CaO·Si_2N_2O,在3CaO·Si_2N_2O 和3CaO·Al_2O_3两化合物之间形成连续立方固溶体。而 Si_2N_2O-Al_2O_3-La_2O_3系统中则没有发现新化合物。在两个系统的富 Si_2N_2O区,过量的 Si_2N_2O 与 La_2O_3和 CaO 分别反应形成 Si_3N_4与 La_(10)[SiO_4]_(?)N_2(H-相)(和 CaSiO_3。所研究的这两个三元系统中,分别形成了如下几个四元相容性区。在 Si_2N_2O-Al_2O_3-La_2O_3系统内有:H-Si_3N_4-La_2O_3·Si_2N_2O-La_2O_3·Al_2O_3;H-Si_3N_4-La_2O_3·Al_2O_3-La_2O_3·11 Al_2O_3;H-Si_3N_4-La_2O_3·11 Al_2O_3-Al_2O_3;H-Si_3N_4-Al_2O_3-O′s.s;H-Si_3N_4-O′s.s-Si_2N_2O在 Si_2N_2O-Al_2O_3-CaO 系统内有:Si_3N_4-CaSiO_3-CaO·Si_2N_2O-3CaO·Al_2O_3;Si_3N_3-CaSiO_3-3CaO·Al_2O_3-2CaO·Al_2O_3·SiO_(?);Si_(?)N_(?)-CaSiO_3-2CaO·Al_2O_3·SiO_2-Al_2O_3;Si_3N_4-CaSiO_3-Al_2O_(?)-O′s.s;Si_3N_4-CaSiO_3-O′s.s-Si_(?)N_(?)O 相似文献