Investigation of the Emission Cross-sections and the Spectra of (Cr~(4 ), Yb~(3 ) ): YAG Crystal

l introductionIn recent years, Cr4 --doped crystals have attracted a great deal of attention aspassive Q--,wit,h.,[l~4]. These Cr4 --dOPed crystals include Cr4 : YAG[l'21 ) Cr4 :GSGG[s], Cr4 : YSO['] etc. They have a large absorption cross section and lOwsaturable intensity at the laser wavelength. In comparison with previously usedsaturable absorbers such as dyes['] and LiF: FZ-- [6] cOlor center crystals, Cr4 -dopedcrystals are more photO--chemically and thermally stable and h…     

Photoluminescence studies of NaCaPO4:RE (RE=Dy, Mn or Gd)

The purpose of the present study is to develop an understanding of photoluminescence properties of Dy³⁺, Mn²⁺ or Gd³⁺doped NaCaPO₄ phosphors, which have served as efficient phosphors in many industrial applications. The phase formation was confirmed by the X-ray powder diffraction (XRD) measurement. Photoluminescence (PL) excitation spectrum measurement of NaCaPO₄:Dy³⁺ shows this phosphor can be efficiently excited by near-ultraviolet (UV) light from 300 to 400 nm and presents dominant luminescence band centered at 480 nm (blue) and 573 nm (yellow). The PL excitation of NaCaPO₄:Mn²⁺ and Gd³⁺ under UV wavelength shows the emissions at 520 and 313 nm, respectively. A scanning electron microscope (SEM) shows an average crystallite size in sub-micrometer range. The obtained results show that the phosphors have the potential for application in the lamp industry and medical applications.     

Eu^3＋离子在晶体KY3F10,YPO4及YVO4中的角重迭晶场参数计算

本文运用角重迭模型首次对Eu~(3+)离子在KY_3F_(10)S、YPO_4及YVO_4晶体中的四个角重迭参数e_σ、e_π、e_δ、e_φ进行了计算。结果表明,所得规律与文献[1]基本相符,并且e_σ和e_φ两个参数对能级的劈裂和移动也有着不可忽略的作用。     

Tripolyphosphate as Precursor for REPO4:Eu3+ (RE = Y, La, Gd) by a Polymeric Method

A modification of the Pechini method was applied to obtain luminescent rare earth orthophosphates. The developed synthetic route is based on the ability of the tripolyphosphate anion () to act both as a complexing agent and as an orthophosphate precursor. Heating of aqueous solutions containing RE³⁺, Eu³⁺, , citric acid, and ethylene glycol led to polymeric resins. The ignition of these resins at different temperatures yielded luminescent orthophosphates. The produced nanosized phosphors (YPO₄:Eu³⁺, (Y,Gd)PO₄:Eu³⁺, and LaPO₄:Eu³⁺) were analyzed by infrared and luminescence spectroscopies, X-ray diffractometry, and scanning electron microscopy.     

Spectroscopy of YAl3(BO3)4:Cr3+ crystals following first principles and crystal field calculations

The CASTEP module of the Materials Studio package was used for calculations of the structural, electronic and optical properties of pure and Cr³⁺-doped YAl₃(BO₃)₄ (YAB). The exchange-correlation effects were treated within the generalized gradient approximation with the Perdew–Burke–Ernzerhof functional. The Monkhorst–Pack scheme k-points grid sampling was set at 3?×?3?×?4 for the Brillouin zone. The plane-wave basis set energy cutoff was set at 340?eV; ultrasoft pseudopotentials were used for all chemical elements. The convergence parameters were as follows: total energy tolerance 1?×?10^?5?eV/atom, maximum force tolerance 0.03?eV/nm, maximal stress component 0.05?GPa and maximal displacement 0.001?Å. The principal absorption peaks of the studied crystal were identified. The influence of 532?nm?cw, 300?mW laser radiation on the observed absorptions was studied.     

Passively Q-switched self-frequency doubling Nd~(3+):ReCa_4O(BO_3)_3(Re=Y,Gd) lasers with tin diselenide as a saturable absorber

With tin diselenide(SnSe_2) film as a saturable absorber(SA), the passively Q-switched self-frequency doubling(SFD) lasers were realized in Nd~(3+):ReCa_4O(BO_3)_3(Re = Y, Gd) crystals. For Nd:YCa_4O(BO_3)_3 crystal, the maximum average output power at 532 nm was 19.6 mW, and the corresponding pulse repetition frequency, pulse duration, single pulse energy, and peak power were 17.6 kHz, 91.9 ns, 1.1 μJ, and 12.1 W, respectively. For Nd:GdCa_4 O(BO_3)_3 crystal, these values were 14.5 mW, 22.1 kHz, 48.7 ns, 0.66 μJ, and 13.5 W.     

Shaped crystal growth and scintillating properties of Yb:(Gd,Lu)3Ga5O12 solid solutions

Shaped single crystals of (Lu_xGd_1−x)₃Ga₅O₁₂ (0.0x1.0) and (Yb_0.05Lu_xGd_0.95−x)₃Ga₅O₁₂ (0.0x0.9) were grown by the modified micro-pulling-down method. Continuous solid solutions with garnet structure and a linear compositional dependency of crystal lattice parameter in the system Yb:(Gd,Lu)₃Ga₅O₁₂ are formed. Measured optical absorption spectra of the samples show 4f–4f transitions related to Gd³⁺ ion at 275 and 310 nm, and also an onset of charge transfer transitions from oxygen ligands to Gd³⁺ or Yb³⁺ cations below 240 nm. A complete absence of Yb³⁺ charge transfer luminescence under X-ray excitation in any of the investigated samples was explained by the overlapping of charge transfer absorption of Yb³⁺ by that of Gd³⁺ ions. For specific composition of Lu_1.5Gd_1.5Ga₅O₁₂ an intense defect-host lattice-related emission, which achieve of about 40% integrated intensity compared with Bi₄Ge₃O₁₂, was found.     

Synthesis,structural study and thermal behaviour of a new compound: trirubidium bis(hydrogen sulphate) dihydrogen arsenate Rb3(HSO4)2.5(H2AsO4)0.5

Mixed crystals Rb₃(HSO₄)_2.5(H₂AsO₄)_0.5 have been prepared by slow evaporation from aqueous solution at room temperature. The crystals were characterized by X-ray single analysis, which revealed that Rb₃(HSO₄)_2.5(H₂AsO₄)_0.5 crystallizes in the space group P with lattice parameters: a = 7.471(3) Å; b = 7.636(1) Å; c = 12.193(2) Å; α = 71.91(1)°; β = 73.04(6)° and γ = 88.77(2)°. In this structure, the ordered S(1)O₄ and the disordered S(3)/AsO₄ tetrahedra are connected by O–H..O hydrogen bonds, to a zigzag chains running in the b-direction. These chains are, in turn, bonded to one another by disordered hydrogen bridges O–H..H–O, to give a planar structure, with hydrogen-bonded sheets, laying parallel to (1 0 0). Each disordered tetrahedron is linked to a tetrahedron neighbouring S(2)O₄ by ordered hydrogen bonds. Broader peaks in IR spectrum of the title material support the assumption of disordered structure. Thermal analysis of the superprotonic transition in Rb₃(HSO₄)_2.5(H₂AsO₄)_0.5 showed that the transformation to the high-temperature phase occurs by one-step process at 404 K. Thermal decomposition of this compound takes place at much higher temperatures, with an onset of approximately 473 K.     

Two potassium rare-earth polyphosphates KLn(PO3)4 (Ln=Ce, Eu): Structural, optical, and electronic properties

Two potassium rare-earth polyphosphate single-crystals KLn(PO₃)₄ (Ln=Ce (1), Eu (2)) have been synthesized by the high-temperature solution reaction and characterized by single-crystal X-ray diffraction. The two isostructural compounds crystallize in the monoclinic system with space group P2₁, and all cell parameters shrink with the decrease of Ln³⁺ ion radius. The main structural feature is (PO₃)₄⁴⁻ wavy chains and infinite tunnels delimited by LnO₈ and KO₈ polyhedra. The energy band structures, density of states (DOS), and optical response functions for 1 have been calculated with the density functional theory (DFT) method, and the dielectric functions and refractive indices have been discussed. The measurements of the absorption and emission spectra show that 1 exhibits the ultraviolet emissions, and 2 displays the characteristic yellow-red emissions of Eu³⁺.     

Studies of structure, thermal, and electrical properties for Cs 5 H 3 (SO 4 ) 4 crystal

Electrical conductivity, differential scanning calorimetry, and X-ray diffraction measurements were performed on a pentacesium trihydrogen tetrasulfate, Cs₅H₃(SO₄)₄, crystal. The transition entropy at a superionic phase transition and the activation energy of proton migrations in the superionic phase were determined to be 58.2 J K⁻¹ mol⁻¹ and 0.48 eV, respectively. The crystal structure of Cs₅H₃(SO₄)₄ at room temperature was refined. The electrical conduction in Cs₅H₃(SO₄)₄ was discussed with the refined structure.     

EXAFS study of intermetallics of the type RGe2 (R=La,Ce, Pr,Nd, Sm,Gd, Tb,Dy, Ho,Er and Y) Part II: Determination of Ge-R distances

The extended x-ray absorption fine structure (EXAFS) associated with the GeK x-ray absorption discontinuity in pure germanium and in the intermetallics RGe₂ (R=La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er and Y) has been studied. The Ge-R distances in these compounds have been determined by comparing the experimental phase shifts with the theoretical ones. The Ge-R distances in the compounds TbGe₂, HoGe₂ and ErGe₂ are being reported for the first time in this work.     

EXAFS study of intermetallics of the type RGe2 (R=La,Ce, Pr,Nd, Sm,Gd, Tb,Dy, Ho,Er and Y) Part I: Determination of Ge-Ge distances

A study of theEXAFS associated with theK x-ray absorption discontinuity of germanium in pure germanium and in the rare-earth germanides RGe₂ (where R=La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er and Y) has been carried out. The Ge-Ge distances have been obtained in these compounds. Considering the phase to the RGe₂ system, the bond lengths in these compounds have been determined. The values obtained by us for the RGe₂ compounds (R=La, Ce, Pr, Nd, Sm, Gd, Dy and Y) agree with those obtained earlier by crystallographic methods. The bond lengths for the compounds TbGe₂, HoGe₂ and ErGe₂ are also being reported.     

Engineering lattice matching, doping level, and optical properties of KY(WO4)2:Gd, Lu, Yb layers for a cladding-side-pumped channel waveguide laser

Single-crystalline KY_1?x?y?z Gd_xLu_yYb_z(WO₄)₂ layers are grown onto undoped KY(WO₄)₂ substrates by liquid-phase epitaxy. The purpose of co-doping the KY(WO₄)₂ layer with suitable fractions of Gd³⁺ and Lu³⁺ is to achieve lattice-matched layers that allow us to engineer a high refractive-index contrast between waveguiding layer and substrate for obtaining tight optical mode confinement and simultaneously accommodate a large range of Yb³⁺ doping concentrations by replacing Lu³⁺ ions of similar ionic radius for a variety of optical amplifier or laser applications. Crack-free layers, up to a maximum lattice mismatch of ~0.08 %, are grown with systematic variations of Y³⁺, Gd³⁺, Lu³⁺, and Yb³⁺ concentrations, their refractive indices are measured at several wavelengths, and Sellmeier dispersion curves are derived. The influence of co-doping on the spectroscopy of Yb³⁺ is investigated. As evidenced by the experimental results, the lattice constants, refractive indices, and transition cross-sections of Yb³⁺ in these co-doped layers can be approximated with good accuracy by weighted averages of data from the pure compounds. The obtained information is exploited to fabricate a twofold refractive-index-engineered sample consisting of a highly Yb³⁺-doped tapered channel waveguide embedded in a passive planar waveguide, and a cladding-side-pumped channel waveguide laser is demonstrated.     

(Eu2+,Nd3+): CaAl2O4的长余辉发光及机理的研究

采用高温固相反应法制备了Eu²⁺: CaAl₂O₄、(Eu²⁺,Nd³⁺): CaAl₂O₄, 等系列材料.测量了其激发、发射光谱及余辉衰减曲线.分析了掺杂稀土离子对长余辉发光的作用.并对其发光机理进行了深入地探讨.     

In situ pressure-induced solid-state amorphization in Sm2(MoO4)3, Eu2(MoO4)3 and Gd2(MoO4)3 crystals: chemical decomposition scenario

The effect of pressure on the phase transformations in Sm₂(MoO₄)₃, Gd₂(MoO₄)₃ and Eu₂(MoO₄)₃ crystals has been studied in situ using synchrotron radiation. All three isostructural compounds undergo a structural phase transition at 2.2-2.8 GPa to a new phase, which is interpreted as a possible precursor of amorphization. Amorphization in these crystals occurs irreversibly over a wide pressure range, and its mechanism, interpreted as a chemical decomposition, is found to be weakly affected by the degree of hydrostaticity.     

Effects of pressure on the two polymorphs of [Co(NH3)5NO2]I2: The anisotropy of lattice distortion and a phase transition

Abstract

The effect of pressure on the two polymorphs of [CO(NH₃)₅NO₂]I₂ (phase I-orthorhombic, S.G. Pnma; phase II-monoclinic, S.G. C2/m) was studied by X-ray powder diffraction in a diamond anvil cell (DAC). In the presence of the ethanol-methanol-water mixture used as a pressure-transmitting liquid polymorph I was shown to undergo a phase transition at pressures between 0.45 GPa and 0.65 GPa. The diffraction pattern of the high-pressure phase (phase III) could be indexed as tetragonal with lattice parameters similar to those, which were previously reported for polymorph II in a 'pseudotetragonal setting'. The lattice distortions of phases II and III were studied at pressures up to 3.2 GPa and 3.7 GPa, correspondingly, and were shown to be very similar. Phases II and III were supposed to be very closely related. If poly(chlortrifluorethylen)-oil was used as a pressure-transmitting medium, no phase transitions were observed in phase I of [CO(NH₃)₅NO₂I₂ at least up to 1.8 GPa (the point when poly(chlortrifluorethylen)-oil becomes solid), and the anisotropy of lattice distortion could be measured.     

Theoretical investigations on the spin Hamiltonian parameters and local structures for the trigonal Ni2+ centers in CsMgX3 (X=Cl,Br, I)

The spin Hamiltonian parameters (zero-field splitting and the anisotropic g factors) and the local structures for the trigonal Ni²⁺ centers in CsMgX₃ (X=Cl, Br, I) are theoretically investigated from the perturbation formulas of these parameters for a 3d⁸ ion in trigonally distorted octahedra, by including the ligand s-orbital contributions. Based on the studies, the local impurity-ligand bond angles β related to the C ₃ axis in the Ni²⁺ centers are found to be about 2° larger than the corresponding angles, β_H, in the hosts, due to the size mismatching substitution of Mg²⁺ by Ni²⁺. The theoretical results based on the inclusion of the ligand s-orbital contributions show an improvement when compared with those in the absence of the above contributions, especially for the ligand I^?.     

Charge transfer transitions in the transition metal oxides ABO4:Ln and APO4:ln (A=La, Gd, Y, Lu, Sc; B=V, Nb, Ta; Ln=lanthanide)

We have compiled and analyzed optical and structural properties of lanthanide doped non-metal oxides of the form APO₄:Ln³⁺ with A a rare earth and of transition metal oxides with formula ABO₄:Ln³⁺ with B a transition metal. The main objective is to understand better the interrelationships between the band gap energy, the O²⁻→Ln³⁺ charge transfer energy, and the Ln³⁺→B⁵⁺ inter-valence charge transfer energy. Various models exist for each of these three types of electron transitions in inorganic compounds that appear highly related to each other. When properly interpreted, these optically excited transitions provide the locations of the lanthanide electron donating and electron accepting states relative to the conduction band and the valence band of the hosting compound. These locations in turn determine the luminescent properties and charge carrier trapping properties of that host. Hence, understanding the relationship between the different types of charge transfer processes and its implication for lanthanide level location in the band gap is of technological interest.     

钒磷酸钇铕PDP用荧光粉的合成及其发光特性研究

采用共沉淀法成功合成了Y（P,V）O4：Eu^3＋荧光粉,并利用SEM、变温紫外激光激发及真空紫外激发下的发射光谱对所合成粉体的表面形貌及发光性能进行了表征。试验结果表明,与高温固相合成法相比,共沉淀法合成的Y（P,V）O4：Eu^3＋荧光粉的颗粒形貌好,发光强度明显提高;在325nm激光激发下,低温时存在基质VO4^3-的蓝色宽带发射,随着温度升高,VO4^3-吸收的激发能量逐渐传递给Eu^3＋,使其发光逐渐增强,当温度高于临界点时,Eu^3＋发射出现温度猝灭;Y（P,V）O4：Eu^3＋荧光粉发射主峰位于619nm,色纯度好,且发光亮度与彩色PDP用商品红粉（Y,Gd）BQ：Eu^3＋相当。