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Structures and luminescence properties of Yb3+ in the double perovskites Ba2YB'O6 (B'=Ta5+, Nb5+) phosphors 下载免费PDF全文
The Yb3+ doped Ba2YB'O6 (B'=Ta5+, Nb5+) were prepared by high temperature solid-state reaction method, their structures were determined by x-ray diffraction and refined by Rietveld method. The diffuse reflection absorption, excitation and emission spectra of Yb3+:Ba2YB'O6 (B'=,Ta5+, Nb5+) were measured at room temperature. Under the excitation of ultraviolet light, these phosphors exhibit broad charge transfer band emissions of TaO6 or NbO6 centre with large Stokes shift. The Yb3+ doped into these hosts are situated at Y3+ sites of cubic symmetry (Oh). The experimental energy levels of Yb3+ in Ba2YTaO6 and Ba2YNbO6 were determined by photoluminescence and diffuse reflection absorption spectra. Their wavefunctions and theoretical energy levels were obtained by diagonalising the Hamiltonian matrix. The experimental energy levels were fitted by Levenberg--Marquardt iteration algorithm to determine crystal field parameters. Then, the magnetic-pole transition line strengths of Yb3+:Ba2YB'O6(B'=Ta5+, Nb5+) from (2F5/2)Γ8- to the low-energy states were calculated. 相似文献
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Method for fitting crystal field parameters and the energy level fitting for Yb3+ in crystal Sc2O3 下载免费PDF全文
<正>A method to compute the numerical derivative of eigenvalues of parameterized crystal field Hamiltonian matrix is given,based on the numerical derivatives the general iteration methods such as Levenberg-Marquardt,Newton method, and so on,can be used to solve crystal field parameters by fitting to experimental energy levels.With the numerical eigenvalue derivative,a detailed iteration algorithm to compute crystal field parameters by fitting experimental energy levels has also been described.This method is used to compute the crystal parameters of Yb~(3+) in Sc_2O_3 crystal, which is prepared by a co-precipitation method and whose structure was refined by Rietveld method.By fitting on the parameters of a simple overlap model of crystal field,the results show that the new method can fit the crystal field energy splitting with fast convergence and good stability. 相似文献
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以反滴定共沉淀方法制备了Sc2O3:Nd、Sc2O3 :Yb纳米粉体,用热重、差热分析、X射线衍射对前驱体相变及粉体结构进行了研究,并研究了其光致发光.Sc2O3:Nd、 Sc2O3:Yb前躯体的热重和差热曲线分别在73 ℃、77 ℃与434 ℃、436 ℃出现了明显的热失重和吸热峰,结合XRD表明约在450 ℃,前驱体粉体经γ-ScOOH相转变为立方Sc2O3相.Reitveld方法精修给出Sc、O的原子坐标.结果表明,掺杂离子导致了晶格畸变.在825 nm光激发下,粉体Sc2O3 :Nd的1084 nm主荧光峰为Nd3+的4F3/2→4I11/2跃迁;在937 nm光激发下,粉体Sc2O3:Yb的1044 nm主荧光峰为Yb3+的2F5/2→2F7/2跃迁.Sc2O3:Nd、Sc2O3:Yb的发光光谱表明激活离子处于较强晶场中,Stark能级分裂大,有利于降低Yb3+的激光阈值、提高激光热稳定性. 相似文献
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Calculating Hamiltonian parameters for Yb~(3+) in a low-symmetry lattice site,and fitting the structure and levels of Yb~(3+) :TaO_4 (= Gd,Y,and Sc) 下载免费PDF全文
An iterative method is used to find the values of the Hamiltonian parameters for Yb3+ in a given low-symmetry crystalline site.Samples of Yb3+:RETaO4(RE = Gd,Y,and Sc) were prepared and their structures were determined.Based on the obtained structural data,their orbital-spin parameters and crystal field parameters were fitted by the superposition model(SM).Using the crystal field parameters obtained by the SM fitting as the initial parameters,the Hamiltonian parameters were fitted iteratively.The calculated and experimental energy levels for Yb3+:RETaO4 are consistent,and the maximal mean-root-square deviation is only 2.84 cm-1,indicating that the method is effective to determine the Hamiltonian parameters of Yb3+ in low-symmetry crystalline sites. 相似文献
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Calculating Hamiltonian parameters for Yb^3+ in a low-symmetry lattice site, and fitting the structure and levels of Yb^3+ :RETaO4 (RE = Gd, Y, and Sc) 下载免费PDF全文
An iterative method is used to find the values of the Hamiltonian parameters for Yb^3+ in a given low-symmetry crys- talline site. Samples of Yb^3+ :RETaO4 (RE = Gd, Y, and Sc) were prepared and their structures were determined. Based on the obtained structural data, their orbital-spin parameters and crystal field parameters were fitted by the superposition model (SM). Using the crystal field parameters obtained by the SM fitting as the initial parameters, the Hamiltonian parameters were fitted iteratively. The calculated and experimental energy levels for Yb^3+:RETaO4 are consistent, and the maximal mean-root-square deviation is only 2.84 cm^- 1, indicating that the method is effective to determine the Hamiltonian parameters of Yb^3+ in low-symmetry crystalline sites. 相似文献
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