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1.
在真空紫外光激发下,六万结构的NaGdF4:Eu3+中的Gd3+离子吸收一个光子,将能量分两步传递给Eu3+离子,发生红色双光子发射.立方结构的NaGdF4:Eu3+中存在一定量的氧离子取代缺陷,使Gd3+离子4f-5d跃迁移到177nm附近,这与惰性气体放电产生的VUV光波长一致,并且其荧光色纯度较高.在VUV激发下,GdBaB9O16中的Gd3+离子发生双光子(紫外和红色或远红外)发射.  相似文献   

2.
采用固相反应法制备了SrMn0.5Fe0.5O3陶瓷样品,并对样品的晶体结构,磁性和离子价态进行了系统的表征与分析. X射线衍射谱的Rietveld拟合表明样品属于理想的立方钙钛矿型结构,Mn离子和Fe离子随机占据B位的O八面体中心. X射线光电子能谱表明Mn离子为+3和+4的混合原子价态,Fe离子为+3价. 样品在大于230K的高温区域呈现Curie顺磁特性,在小于230 K的低温区域样品表现出自旋玻璃态行为,这种特性源于Mn离子和Fe离子之间的交换作用及自身价态和分布的不均匀性. 由于Fe3+离子占据O八面体的中心,对顺磁区的Mssbauer谱测量表现为四级分裂.  相似文献   

3.
余万伦 《中国物理》1993,2(8):610-618
This paper presents high-order perturbation calculations for the zero-field splitting parameters D, F, and a of Fe3+-VCd pairs in RbCdF3 and CsCdF3 crystals doped with Fe3+ impurities. In comparison with experimental data, the present results are better than those obtained in previous work by using the phenomenological su-perposition model of spin-Hamiltonian. Moreover, the crystal fields arising from the Cd2+-vacancy and their induced crystal lattice distortion are analysed and calculated. It is found that the contribution from the Cd2+-vacancies cannot be ignored. Mena-while, we obtain that a ligand F- along the [001]-axis moves towards the central Fe3+ ion by Δ= 0.0020nm in RbCdF3 and 0.0028nm in CsCdF3. These results are quite different from Δ = 0.0104nm and Δ = 0.0112nm, respectively, obtained in previous work by using the superposition model of spin-Hamiltonian and ignoring the effect of the vacancy.  相似文献   

4.
Er3+单掺及Er3+/Yb3+共掺SiO2-Al2O3-La2O3玻璃光谱性质研究   总被引:10,自引:4,他引:6  
研究了单掺Er3+及Er3+/Yb3+共掺SiO2-Al2O3-La2O3玻璃的光谱性质随稀土离子浓度变化规律,应用McCumber理论计算了玻璃在1.53 μm的发射截面及积分吸收截面.结果表明:在Er3+离子掺杂浓度相同时,玻璃在980 nm吸收截面与Yb3+掺杂浓度成反比;当样品中Yb3+离子掺杂浓度为3.94×1020 cm-3时,玻璃在1.53 μm的吸收截面和发射截面最大,在1.40~1.60 μm积分吸收截面也最大;Er3+/Yb3+共掺SiO2-Al2O3-La2O3玻璃在1.53 μm的荧光半高宽随Er3+掺杂浓度升高而增加,当Er3+离子掺杂浓度为2.41×1020 cm-3时,玻璃的荧光半高宽(FWHM)达到52.5 nm.  相似文献   

5.
采用高温熔融法制备了组分为TeO2-ZnO-Na2O的Tm3+离子单掺和Tm3+/Yb3+共掺碲酸盐玻璃,应用Judd-Ofelt理论计算分析了玻璃样品的强度参量Ωt(t=2, 4, 6),自发辐射跃迁几率A,荧光分支比β和荧光辐射寿命τrad等光谱参量,测量得到了不同Yb3+离子掺杂浓度下玻璃样品的Tm3+离子上转换发光谱.结果显示,在980 nm泵浦光激励下玻璃样品发射出强烈的近红外上转换荧光.对Tm3+离子上转换发光分析表明,强烈的Tm3+离子近红外上转换发光主要来自于Yb3+/Yb3+离子间的共振能量传递以及基于单声子和双声子辅助的Yb3+/Tm3+离子间的非共振能量传递过程,并进一步计算得到了声子贡献比和能量传递系数.最后,计算分析了Tm3+:3F43H6能级间跃迁的1.8 μm波段吸收截面、受激发射截面和增益系数.研究表明,Yb3+/Tm3+共掺TeO2-ZnO-Na2O玻璃可以作为近红外波段固体激光器的潜在增益基质.  相似文献   

6.
The Mn cation distribution in the seven sublattices of theW-type structure has been determined from high temperature neutron diffraction data of a SrMn2Fe16O27 powder sample. The Mn2+ ions enter the tetrahedral sites of blockS with a preference for site 4e. Mn3+ ions in small amounts are found in the octahedral sites, substituting for Fe3+, while 0.3 Fe2+ has been found in site 6g. The sample has the formula SrMn2.4Fe15.6O27. The crystal structure has been described in the non-centrosymmetric Pˉ62c space group, instead of the usual P63/mmc one. The magnetic structure, obtained from low temperature (4.2 K) data, is collinear, with the spins parallel to thec axis, according to the Gorter model. The magnetic moments of the sites give an experimental magnetization valueM s=28.4(1.5) μB/f.u., in good agreement with magnetic measurements and the theoretical value.  相似文献   

7.
欧阳楚英  雷敏生 《光子学报》2001,30(10):1279-1282
本文以Cr3+自由离子的3d电子径向波函数为基础,对Cr3+:Al2O3中的电子云延伸效应进行了理论研究,引入了电子云延伸效应系数κ,得到了Cr3+:Al2O3中Cr3+离子的最优化3d电子径向波函数.并研究了压力对电子云延伸效应系数κ的影响.  相似文献   

8.
Ce3+ 掺杂高密度氧化物玻璃的闪烁性能研究   总被引:2,自引:0,他引:2       下载免费PDF全文
杨斌  张约品  徐波  来飞  夏海平  赵天池 《物理学报》2012,61(19):192901-192901
用高温熔融法制备了以SiO2-B2O3-Al2O3-Gd2O3为基质系统Ce3+掺杂的玻璃样品, 测试样品的密度、紫外——可见透射光谱、紫外激发光谱和主要的闪烁性能, 并且把一部分闪烁性能和PbWO晶体及BGO晶体做比较. 着重研究了不同Ce3+掺杂浓度与Gd3+ 离子的含量对玻璃样品闪烁性能的影响规律. 结果表明: 玻璃样品具有较大的密度; 样品的X射线激发发射光谱发射峰位置都在390 nm左右, 当Ce3+ 离子的掺杂浓度为1.0 mol%(摩尔分数)、Gd2O3含量为15 mol%时, 玻璃样品的发光峰强度达到BGO晶体发光强度的90%; 同样验证了Ce3+ 离子具有浓度猝灭效应; Gd3+可以敏化Ce3+离子发光, 但是Gd3+离子到达一定浓度时, 反而会产生猝灭效应, 降低了Ce3+ 离子的发光. Ce3+ 离子掺杂SiO2-B2O3-Al2O3-Gd2O3系统的闪烁玻璃有望替代闪烁晶体广泛应用于高能物理中.  相似文献   

9.
宋桂林  周晓辉  苏健  杨海刚  王天兴  常方高 《物理学报》2012,61(17):177501-177501
采用快速液相烧结法制备BiFeO3和Bi0.95Gd0.05Fe1-xCoxO3 (x= 0, 0.05, 0.1, 0.15, 0.2)陶瓷样品,研究Gd, Co共掺杂对BiFeO3微观结构, 介电性能和铁磁性的影响. X射线衍射谱表明:所有样品的主衍射峰与纯相BiFeO3相符合且 具有良好的晶体结构,随着Co3+掺杂量x的增大, Bi0.95Gd0.05Fe1-xCoxO3样品的主衍射峰(104)与(110)逐渐相互重叠, 当x大于0.1时, 样品呈现正方晶系结构; J-V特性显示Gd3+, Co3+共掺杂有效地降低BiFeO3陶瓷的漏导电流,其降低幅度为1-2个数量级; 当f=103 Hz时, Bi0.95Gd0.05Fe0.8Co0.2O3的介电常数是BiFeO3的6倍, 而Bi0.95Gd0.05Fe0.95Co0.05O3和 Bi0.95Gd0.05Fe0.85Co0.15O3样品的介电损耗最小,均为0.01.室温下, Bi0.95Gd0.05Fe1-xCoxO3样品磁性与BiFeO3相比显著增强. 在磁场为30 kOe的作用下,Bi0.95Gd0.05Fe1-xCoxO3 (x= 0, 0.05, 0.1, 0.15, 0.2)的剩余磁化强度Mr分别是BiFeO3的34, 60, 105, 103, 180倍.样品磁性增强的主要原因是Gd, Co掺杂使BiFeO3的晶格结构发生变化导致BiFeO3自身储存的磁性能被释放, Gd3+的4f电子与Fe3+或Co3+的3d电子自旋相互作用及样品中存在局域的 Fe-O-Co磁耦合三者共同作用的结果.  相似文献   

10.
王森  周亚训  戴世勋  王训四  沈祥  陈飞飞  徐星辰 《物理学报》2012,61(10):107802-107802
采用高温熔融退火法制备了系列 80TeO2-10Bi2O3-10TiO2-0.5Er2O3-xCe2O3 (x=0,0.25, 0.5,0.75,1.0 mol%)和(80-y) TeO2-10Bi2O3-10TiO2-yWO3-0.5Er2O3-0.75Ce2O3 (y=3,6,9,12 mol%)的碲铋酸盐玻璃.测试了玻璃样品400-1700 nm范围内的吸收光谱, 975 nm抽运下的上转换发光谱和1.53 μm波段荧光谱, 以及808 nm激励下的Er3+离子荧光寿命和无掺杂玻璃样品的Raman光谱, 并结合Judd-Ofelt理论和McCumber理论计算了Er3+离子光谱参数.结果表明, 在掺Er3+碲铋酸盐玻璃中引入Ce3+离子进行Er3+/Ce3+共掺, 通过Er3+离子4I11/2能级与Ce3+离子2F5/2 能级间基于声子辅助的能量传递过程,可以有效抑制Er3+离子上转换发光并明显增强其 1.53 μm波段荧光;同时,在现有Er3+/Ce3+共掺玻璃组分基础上引入WO3, 可进一步提高1.53 μm波段荧光并展宽其荧光发射谱. 研究结果对于获取优异光谱特性的宽带掺Er3+光纤放大器玻璃基质具有实际意义.  相似文献   

11.
A single-crystal TlGaSe2 doped by paramagnetic Fe ions has been studied at room temperature by electron paramagnetic resonance (EPR) technique. The fine structure of EPR spectra of paramagnetic Fe3+ ions was observed. The spectra were interpreted to correspond to the transitions among spin multiplet (S=5/2, L=0) of Fe3+ ion, which are splitted by the local ligand crystal field (CF) of orthorhombic symmetry. Four equivalent Fe3+ centers have been observed in the EPR spectra and the local symmetry of crystal field at the Fe3+ site and CF parameters were determined. Experimental results indicate that the Fe ions substitute Ga at the center of GaSe4 tetrahedrons, and the rhombic distortion of the CF is caused by the Tl ions located in the trigonal cavities between the tetrahedral complexes.  相似文献   

12.
TlGaS2 single crystal doped by paramagnetic Fe3+ ions has been studied by electron paramagnetic resonance (EPR) technique. The fine structure of EPR spectra of paramagnetic Fe3+ ions was observed. The spectra reveal a nearly orthorhombic symmetry of the crystal field (CF) on the Fe3+ ions. Two groups each consisting of four equivalent Fe3+ centers were observed in the EPR spectra. The local symmetry of the crystal field on the Fe3+ centers and CF parameters were determined. Experimental results indicate that the Fe ions substitute Ga at the center of the GaS4 tetrahedrons. The rhombic distortion of the sulfur ligand CF is attributed to the effect of Tl ions located in the trigonal cavities between the tetrahedral complexes. The observed twinning of the resonance lines indicates a presence of two non-equivalent positions of Tl ions that confirms their zigzag alignment in the TlGaS2 crystal structure.  相似文献   

13.
The anisotropy spin-orbit coupling matrices for a d5 configuration ion in a trigonal ligand-field have been established. On basis of the anisotropy spin-orbit coupling matrices, the ground state zero-field splitting of the Fe3+ ions in ilmenite-structure MgTiO3:Fe3+ system has been studied. The calculated results show that the anisotropy of Fe3+ ions in the diamagnetic ilmenite MgTiO3 is important and the EPR parameters depend sensitively on the anisotropy divergent parameter. Moreover, the effect of the anisotropy divergent parameter on the second-order parameter D is obviously larger than that on the fourth-order parameter (a-F). Based on this point, the local lattice structure of Fe3+ ion in MgTiO3:Fe3+ system is determined by diagonalizing the complete energy matrices for a d5 configuration ion in a trigonal ligand-field and considering the second-order as well as the fourth-order EPR parameters D and (a-F) simultaneously. Our results are consistent with the experimental proposal that Fe3+ ions may locate at both the Mg2+ and Ti4+ sites.  相似文献   

14.
Electron paramagnetic resonance (EPR) and optical absorption spectral investigations have been carried out on Fe3+ ions doped sodium borophosphate glasses (NaH2PO4-B2O3-Fe2O3). The EPR spectra exhibit resonance signals with effective g values at g=2.02, g=4.2 and g=6.4. The resonance signal at g=4.2 is due to isolated Fe3+ ions in site with rhombic symmetry whereas the g=2.02 resonance is due to Fe3+ ions coupled by exchange interaction in a distorted octahedral environment. The EPR spectra at different temperatures (123-295 K) have also been studied. The intensity of the resonance signals decreases with increase in temperature whereas linewidth is found to be independent of temperature. The paramagnetic susceptibility (χ) was calculated from the EPR data at various temperatures and the Curie constant (C) and paramagnetic Curie temperature (θp) have been evaluated from the 1/χ versus T graph. The optical absorption spectrum exhibits bands characteristic of Fe3+ ions in octahedral symmetry. The crystal field parameter (Dq) and the Racah interelectronic repulsion parameters (B and C) have also been evaluated and discussed.  相似文献   

15.
The results of the nuclear magnetic resonance of 57Fe in Al-, Ga- and In-substituted Y3Fe5O12 garnets are reported. When diamagnetic Ga3+ or Al3+ ions are substituted for tetrahedral Fe3+ ions, four satellite lines in the NMR spectrum of octahedral Fe3+ ions appear. The substitution of In3+ ions for octahedral Fe3+ ions leads to three satellite lines in the spectrum of tetrahedral Fe3+ ions. The hyperfine fields of these satellites are explained using the independent bond model for the hyperfine interaction. Suprisingly large change of the anisotropic part of the hyperfine field relative to the isotropic one was found.  相似文献   

16.
The displacements of Fe3+ ions and hence the structures of Fe3+-Vo defects in ABO3 oxide perovskites are studied by analyzing their electron paramagnetic resonance data from the high-order perturbation formula of zero-field splitting on the basis of the spin-orbit coupling mechanism. The results suggest that the Fe3+ ions in the Fe3+-Vo defect centers are displaced away from the oxygen vacancy Vo by about 0.035 nm. The reasonableness of the displacement is discussed.  相似文献   

17.
Blue-emitting europium-ion-doped MgSrAl10O17 phosphor, prepared using the combustion method, is described. An efficient phosphor can be prepared by this method in a muffle furnace maintained at 500 °C in a very short time of few minutes. The phosphor is characterized by powder X-ray diffraction, scanning electron microscopy, transmission electron microscopy and BET surface area measurements. Photoluminescence (PL) spectra revealed that europium ions were present in divalent oxidation state. The thermoluminescence (TL) glow curve shows two peaks at around 178 and at 354 °C. The defect centres formed in the phosphor are studied using electron spin resonance (ESR). The ESR spectrum indicates the presence of Fe3+ ions in the non-irradiated system. Irradiated MgSrAl10O17:Eu exhibits lines due to radiation-sensitive Fe3+ ion and a defect centre. The centre is characterized by an isotropic g-value of 2.0012 and is assigned to a F+ centre. The radiation-sensitive Fe3+ ion appears to correlate with the main TL peak at 178 °C. During irradiation an electron is released from Fe2+ and is trapped at an anion vacancy to form F+ centre. During heating, an electron is liberated from the defect centre and recombines with Fe3+ emitting light.  相似文献   

18.
An electron paramagnetic resonance (EPR) study of a synthetic single crystal of LiScGeO4 doped with Cr ions carried out earlier at the X- and Q-bands at 300, K has indicated additional weak lines. A detailed analysis of these EPR lines, which were tentatively attributed to the Fe3+ ions at two different mirror symmetry sites, is presented in this paper. The angular dependences in the three crystallographic planes were resolved by fitting the two distinct spectra denoted Fe3+(I) and Fe3+(II) with a spin Hamiltonian (S=5/2) of monoclinic symmetry. The rank-4 crystal field tensors at tetrahedral and octahedral sites were calculated with the point-charge model to determine the principal axis orientations of their cubic, tetragonal and trigonal components. A comparative analysis of the zero-field splitting tensors and the crystal field ones indicates that Fe3+(I) ions substitute for Sc3+ at octahedral sites and Fe3+(II) ions substitute for Ge4+ at tetrahedral sites with no significant distorition of the coordination polyhedra in the structure of LiScGeO4.  相似文献   

19.
Radiolysis‐induced effects on aqueous tungsten ions are observed to form a precipitate within seconds upon exposure to a synchrotron X‐ray micro‐beam in a WO3 + H2O system at 873 K and 200 MPa. In situ Fe K‐edge energy‐dispersive X‐ray absorption spectroscopy (ED‐XAS) measurements were made on Fe(II)Cl2 aqueous solutions to 773 K in order to study the kinetics of high‐temperature reactions of Fe2+ and Fe3+ ions with transient radiolysis species. The radiolytic reactions in a fluid sample within a hydrothermal diamond anvil cell result in oxidation of the Fe2+ ion at 573 K and reduction of Fe3+ at temperatures between 673 and 773 K and of the Fe2+ ion at 773 K. The edge‐energy drift evident in the ED‐XAS data directly reflects the kinetics of reactions resulting in oxidation and/or reduction of the Fe2+ and Fe3+ ions in the aqueous solutions at high temperatures. The oxidation and reduction trends are found to be highly consistent, making reliable determinations of reaction kinetics possible.  相似文献   

20.
GeFe2O4晶体的基态能级和零场分裂参量   总被引:6,自引:0,他引:6       下载免费PDF全文
殷春浩  韩奎  叶世旺 《物理学报》2003,52(9):2280-2283
GeFe2O4是一种单晶化合物,考虑到由3个〈111〉方向之一的一个 轴,从一个中心位置 到另一个中心位置之间,以Fe2+离子为中心离子和O2-为配体构 成了三角(C 3v)对称体系.利用不可约张量理论,建立了3d4/3d6离子三角(C3 v)对称的晶体场和 自旋相互作用哈密顿矩阵,因此,由完全对角化的晶体场和自旋-轨道相互作用哈密顿矩阵 和电子顺磁共振理论公式求出单晶GeFe2O4中Fe2+离子 的电子顺磁共振零场分 裂参量D和F-a.并研究了自旋三重态对电子顺磁共振(EPR)零场分裂的贡献.结果显示自旋 三重态对基态零场分裂的贡献是较强的,理论计算结果与实验值相符. 关键词: 自旋三重态 晶体场 低自旋态 高自旋态 零场分裂  相似文献   

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