Microwave absorption properties regulation and bandwidth formula of oriented Y2Fe17N3-δ@SiO2/PU composite synthesized by reduction-diffusion method

As concepts closely related to microwave absorption properties, impedance matching and phase matching were rarely combined with material parameters to regulate properties and explore related mechanisms. In this work, reduction-diffusion method was innovatively applied to synthesize rare earth alloy Y$_{2}$Fe$_{17}$. In order to regulate the electromagnetic parameters of absorbers, the Y$_{2}$Fe$_{17}$N$_{3-\delta }$ particles were coated with silica (Y$_{2}$Fe$_{17}$N$_{3-\delta }$@SiO$_{2}$) and absorbers with different volume fractions were prepared. The relationship between impedance matching, matching thickness, and the strongest reflection loss peak (${\rm RL}_{\rm min}$) was presented obviously. Compared to the microwave absorption properties of Y$_{2}$Fe$_{17}$N$_{3-\delta }$/PU absorber, Y$_{2}$Fe$_{17}$N$_{3-\delta }$@SiO$_{2}$/PU absorbers are more conducive to the realization of microwave absorption material standards which are thin thickness, light weight, strong absorbing intensity, and broad bandwidth. Based on microwave frequency bands, the microwave absorption properties of the absorbers were analyzed and the related parameters were listed. As an important parameter related to perfect matching, reflection factor ($\sqrt {ărepsilon_{\rm r}/\mu_{\rm r}}$) was discussed combined with microwave amplitude attenuation. According to the origin and mathematical model of bandwidth, the formula of EAB (${\rm RL}<-10$ dB) was derived and simplified. The calculated bandwidths agreed well with experimental results.     

Raman spectrum of decrespignyite [(Y,REE)4Cu(CO3)4Cl(OH)5·2H2O] and its relation with those of other halogenated carbonates including bastnasite,hydroxybastnasite, parisite and northupite

Raman spectroscopy complemented with infrared spectroscopy has been used to study the rare‐earth‐based mineral decrespignyite [(Y,REE)₄Cu(CO₃)₄Cl(OH)₅· 2H₂O] and the spectrum compared with the Raman spectra of a series of selected natural halogenated carbonates from different origins including bastnasite, parisite and northupite. The Raman spectrum of decrespignyite displays three bands at 1056, 1070 and 1088 cm⁻¹ attributed to the CO₃²⁻ symmetric stretching vibration. The observation of three symmetric stretching vibrations is very unusual. The position of the CO₃²⁻ symmetric stretching vibration varies with the mineral composition. The Raman spectrum of decrespignyite shows bands at 1391, 1414, 1489 and 1547 cm⁻¹, whereas the Raman spectra of bastnasite, parisite and northupite show a single band at 1433, 1420 and 1554 cm⁻¹, respectively, assigned to the ν₃ (CO₃)²⁻ antisymmetric stretching mode. The observation of additional Raman bands for the ν₃ modes for some halogenated carbonates is significant in that it shows distortion of the carbonate anion in the mineral structure. Four Raman bands are observed at 791, 815, 837 and 849 cm⁻¹, which are assigned to the (CO₃)²⁻ν₂ bending modes. Raman bands are observed for decrespignyite at 694, 718 and 746 cm⁻¹ and are assigned to the (CO₃)²⁻ν₄ bending modes. Raman bands are observed for the carbonate ν₄ in‐phase bending modes at 722 cm⁻¹ for bastnasite, 736 and 684 cm⁻¹ for parisite and 714 cm⁻¹ for northupite. Multiple bands are observed in the OH stretching region for decrespignyite, bastnasite and parisite, indicating the presence of water and OH units in the mineral structure. Copyright © 2011 John Wiley & Sons, Ltd.     

YTaO4 : Eu,Gd的合成及其发光

采用高温固相反应合成了Y_1-x-yEu_xGd_yTaO₄荧光体,经过XRD证明产物为纯相的M'型YTaO₄结构。通过对样品的光谱测试表明,TaO^3-₄将吸收的能量传递给Eu³⁺,起着一定的敏化作用。掺入少量Gd³⁺对YTaO₄ : Eu的发光有一定的增强作用。用147 nm的真空紫外光激发样品时,样品具有较强的荧光发射,其主发射峰位于612 nm,具有较好的色纯度。     

稀土粉末Eu∶Y_2O_3的自由感应衰减量子拍

稀土固体是重要的激光和光电子材料。目前 ,由于以宽带信号和太赫兹比特数据传输率为特征的信息技术的发展 ,稀土固体材料的相干瞬态动力学过程成为宽带与高速信息光子学的基本物理问题之一。研究了室温下稀土粉末样品Eu3+ ∶Y2 O3自由感应衰减的相干瞬态光谱 ,这有助于理解有效的光吸收动力学、激发态弛豫、相干能量传递和超短光脉冲在稀土固体中的传播。用一对紫外飞秒相干光脉冲作用于稀土粉末样品Eu3+ ∶Y2 O3,然后监测物质激发态的布居数随两个激发脉冲之间的延时的变化 ,测量到其自由感应衰减量子拍 (FID) ,从拍频周期分析确定了其能级精细结构 ,能级的退相时间长达皮秒量级。理论分析和实验结果符合得很好。对稀土离子的量子干涉的研究 ,表明其在受激受控光放大方面具有潜在的应用前景     

一种新型共掺杂稀土配合物的发光特性

制备了一类以苯甲酰水杨酸 (BenzoylSalicylicAcid ,BSA)为第一配体 ,邻菲罗啉 (phenanthroline ,phen)为第二配体的共掺杂稀土铕镧配合物La0 6Eu0 4(BSA) 3 phen。用其作为发光层材料制作了电致发光器件 :ITO/PVK :La0 6Eu0 4(BSA) 3 phen/Alq/Al。讨论并证明了稀土La3 与Eu3 之间存在F rster能量传递。同时将该器件与器件ITO/PVK :Eu(BSA) 3 phen/Alq/Al和ITO/PVK :Tb0 6Eu0 4(BSA) 3 phen/Alq/Al的发光进行了比较。表明该器件具有单色性好 ,整流性好的特性 ,同时得到了最大亮度为 10 2尼特的红光     

稀土氟碳酸盐矿物的光致发光谱和吸收谱研究

测定并讨论了产自四川冕宁矿区的氟碳铈矿和产自内蒙白云鄂博稀土矿区的黄河矿、氟碳钙铈矿、氟碳铈钡矿的光致发光谱。结果表明,稀土氟碳酸盐矿物在488.0nm和514.5nm激光激发下的光致发光中心是Nd3+,发光谱中的所有谱带均出自Nd3+的辐射跃迁。在488.0nm激光激发下,稀土氟碳酸盐矿物在495nm到733nm谱区的发光谱带强而尖锐,但在514.5nm激光激发下,这个谱区的谱带明显变弱或消失,转而出现783nm到907nm谱区的强发光谱带。可见光吸收谱表明稀土氟碳酸盐矿物对可见光的吸收也与矿物中的Nd3+有关。     

稀土氟化物纳/微米材料的水热合成、形成机理和发光性质

研究了稀土氟化物纳/微米材料的设计合成、形貌控制、形成机制以及发光性质.发展了一种简单、整体、没有模板、环境友好的水热方法合成系列稀土氟化物,即用有机添加剂柠檬酸钠(Na3C6H5O7·2H2O)作为配位剂和形貌控制剂,通过改变氟源(NaF,NH4F或NaBF4)和最初溶液的pH值,得到了具有不同成分、晶体结构、尺寸和...     

新型双β-二酮、邻菲罗啉和铕(Ⅲ)三元配合物的合成与发光

合成了一个新型双β-二酮有机配体1,3-双[3-(2-噻吩基)-3-氧代丙酰基]苯、邻菲罗啉和铕的三元配合物,并应用红外光谱、紫外-可见光谱、元素分析和热重-差热分析等对配合物进行了组成确定和结构表征.荧光分析结果表明,配合物612 nm处的发射光谱为中心离子Eu3+的特征红光,属5D0→7F2跃迁带,峰形尖锐,单色性...     

The spectrum of Nd in rare earth orthoaluminates. The trigonal to orthorhombic transition study of the level

Some structural and spectroscopic features of rare earth orthoaluminates are examined.The trigonal→ orthorhombic transition is studied in a series of Nd_xSm_1−xAlO₃ compounds. The evolution of the crystal structure is followed by X-ray analysis and optical absorption. The free ion and crystal field parameters of Nd³⁺ (4f³ configuration) are determined in LuAlO₃:Nd³⁺.The anomaly of the calculated splitting of the levels is slight, but well characterized in NdAlO₃. The spin correlated crystal field and orbitally correlated crystal field models are tested as well as an empirical correction which was proposed earlier.     

Thermal quenching of luminescence in erbium doped semiconductors

The nature of the temperature dependence of luminescence intensity from Er⁺ ions in GaInAsP, Si, InP, GaAs, AlGaAs, ZnTe, as observed by Favennecet al [1] has been examined in terms of a double exponential model. The smaller activation energy is found to be 58–100 meV, characteristic of a localized energy barrier at the Er⁺ centre while the higher activation energy is approximately 0.8E _g attributed to an Auger non-radiative process of carrier excitation into bands. This model has been found to describe the observed temperature dependences with reasonably good agreement.