Ni2+ emission in SrF2

Luminescence measurements of X-irradiated SrF₂:Ni are reported. After X-irradiation two emission bands have been found. One of them peaked at 293 nm and has an excitation band at 267 nm. The other one at about 770 nm, which is much weaker, has an excitation band at 274 nm. Both emission bands are also observed under X-ray excitation. A comparison with some previous studies of the absorption and thermoluminescence properties of X-irradiated SrF₂:Ni indicates that the emission bands are due to two different kinds of Ni²⁺ centers. The proposed emission mechanisms are similar to those found in CaF₂:Ni.     

共掺杂Ce~(3+)调控β-NaLuF_4:Yb~(3+)/Ho~(3+)纳米晶体的上转换荧光发射

在980 nm近红外光激发下,通过共掺杂Ce~(3+)离子调控六方相NaLuF_4:Yb~(3+)/Ho~(3+)纳米晶体的上转换荧光发射.实验结果表明,当掺杂Ce~(3+)离子浓度从0增加到12.0%时,Ho~(3+)离子的上转换荧光发射实现了由绿光向红光的转变,其红绿比提高了近24倍.根据Ho~(3+)离子的能级结构发现,Ho~(3+)离子的红光发射源自~5F_5能级到5I8能级的辐射跃迁,因此要增强红光发射,必须提高该能级粒子数布居.Ho~(3+)与Ce~(3+)离子之间相近的能级差促使它们之间产生了共振交叉弛豫,从而有效地提高了Ho~(3+)离子~5F_5能级的粒子数布居,增强了红光发射.同时对Ho~(3+)离子的上转换调控机理进行讨论,并借助不同的激发策略,进一步证实了Ho~(3+)与Ce~(3+)离子之间相互作用的发生.     

Enhancement of upconversion luminescence of YAlO3:Er3+ by Gd3+ doping

The upconversion luminescences of YAlO3:Er3+ phosphor co-doping with different Gd3+ concentrations are investigated under the excitation of 980- and 532-nm diode lasers. A near ultraviolet upconversion emission at 410 nm is observed in YAlO3 under 532-nm excitation. Moreover, the inactive Gd3+ ions can improve the upconversion intensity efficiently in a certain range of concentration. Under 980-nm excitation, the visible upconversion emissions at 546 and 646 nm are enhanced by about 10 and 8 times at the Gd3+ concentration of 40%, respectively. The upconversion emission at 410 nm under 532-nm excitation is also enhanced by 7 times. The substitution of Gd3+ ions for Y3+ sites changes the local symmetry of Er3+, leading to the improvement of upconversion efficiency.     

Far infrared absorption of Fe2+ in KMgF3

Far infrared absorption in cubic KMgF₃ doped with Fe²⁺ is reported . A line is observed at 87cm^?1, which is assigned to the (Γ_5g → Γ_3g, Γ_4g) transition in the Fe²⁺. The reduction in the spin-orbit coupling from the free ion value has been predicted by Ham, Schwarz and O'Brien.     

Charge transfer excitation of the Nd3+, Sm3+, Dy3+, Ho3+, Er3+ and Tm3+ emission in CaGa2S4

The excitation spectra of the Nd³⁺, Sm³⁺, Dy³⁺, Ho³⁺, Er³⁺ and Tm³⁺ emission in the sodium-compensated CaGa₂S₄ host lattice, a sulfide with wide band gap, contain an intense band below the absorption edge. Comparison of the energy of its maximum with thermodynamic data and correlations to Jørgensen's refined spin-pairing theory predictions allow one to ascribe this band to a charge transfer transition ending onto 4f orbitals. The irregular variation within the rare earth series contrasts with the monotonic variation of the absorption edge in stoichiometric rare earth sulfides (e.g. NaLnS₂), associated with interband transitions.     

Spectroscopic properties and mechanism of Tm^3＋/Er^3＋/Yb^3＋ co-doped oxyfluorogermanate glass ceramics containing BaF2 nanocrystals

Transparent Tm^3＋/Er^3＋/yb^3＋ co-doped oxyfluorogermanate glass ceramics containing BaF2 nanocrystals are prepared. Under excitation of a 980-nm laser diode （LD）, compared with the glass before heat treatment, the Tm^3＋/Er^3＋/yb^3＋ co-doped oxyfluorogermanate glass ceramics can emit intense blue, green and red up-conversion luminescence and Stark- split peaks; X-ray diffraction （XRD） and transmission electron microscope （TEM） results show that BaF2 nanocrystals with an average diameter of 20 nm are precipitated from the glass matrix. Stark splitting of the up-conversion luminescence peaks in the glass ceramics indicates that Tm^3＋, Er^3＋ and （or） Yb^3＋ ions are incorporated into the BaF2 nanocrystals. The up-conversion luminescence intensities of Tm^3＋, Er^3＋ and the splitting degree of luminescence peaks in the glass ceramics increase significantly with the increase of heat treat temperature and heat treat time extension. In addition, the possible energy transfer process between rare earth ions and the up-conversion luminescence mechanism are also proposed.     

White light generation of glass ceramics containing Ba_2LaF_7：Eu~（2＋）,Tb~（3＋） and Sm~（3＋） nanocrystals

The Eu 2＋ /Tb 3＋ /Sm 3＋ co-doped oxyfluoride glass ceramics containing Ba2LaF7 nanocrystals are prepared in the reducing atmosphere.The X-ray difiraction results show that Eu 2＋ ,Tb 3＋ and Sm 3＋ ions are enriched into the precipitated Ba2LaF7 nanophase after the annealing process.It deduces efficient energy transfers from Eu 2＋ to Tb 3＋ and Sm 3＋ and intenses warm white luminescence of the glass ceramics. Comparing with the glass,the luminescence quantum yield of the glass ceramics is also enlarged by about 3 times.This demonstrates the potential white light-emitting diode application of the glass ceramics produced in this letter.     

纳米晶ZrO2：Eu3＋-Bi3＋的制备及Bi3＋敏化Eu3＋特征发射的研究

采用化学共沉淀法制备了纳米晶ZrO2：Eu3＋-Bi3＋粉体,所制备的纳米晶粉体均能观测到Eu3＋离子的室温特征发射．研究了样品的晶体结构和发光性质．结果表明：经600℃煅烧后得到的纳米晶ZrO2：Eu3＋-Bi3＋粉体的晶相为四方相,经800,950及1100℃煅烧后的样品为四方相和单斜相的混合晶相．Eu3＋离子在四方相中的室温特征发射明显强于在混合相中的发射．Bi3＋离子的掺入对Eu3＋离子的室温特征发射有显著的敏化作用．     

Ni2+ emission in MgO,KMgF3, KZnF3 and MgF2

The emission of Ni²⁺ ions in MgO, KMgF₃, KZnF₃ and MgF₂ crystals has been investigated. The fine structure on the bands at about 20 000 cm^-1 and 13 000 cm^-1 has been studied in detail and from this and the excitation spectra these bands are assigned to ${}^1\text{T}{}_{\mathrm{2g}}\text{→}{}^3\text{A}{}_{\mathrm{2g}}$ and ${}^1\text{T}{}_{\mathrm{2g}}\text{→}{}^3\text{T}{}_{\mathrm{2g}}$ transitions respectively.     

纳米晶ZrO2:Er3+-Yb3+的制备及其室温上转换发射

用化学共沉淀法制备了ZrO₂:Er³⁺-Yb³⁺纳米晶粉体，所制备的纳米晶粉体具有较强的室温上转换发射和红外发射.研究了样品的晶体结构和上转换发光性质随着Yb³⁺掺杂浓度和煅烧温度的变化关系.通过X射线衍射谱分析发现，经800℃煅烧2h后得到的ZrO₂:Er³⁺-Yb³⁺纳米晶是四方相和单斜相的混合结构，经950℃煅烧2h后得到的样品以单斜相为主，随着Y     

Ag+掺杂的立方相Y2O3:Eu纳米晶体粉末发光强度研究

采用化学自燃烧法制备了不同Ag⁺掺杂浓度的Y₂O₃:Eu纳米晶体粉末样品(［Y³⁺］∶［Eu³⁺］∶［Ag⁺］=99∶1∶X，X=0—3.5×10^-2)，以及通过退火处理得到了相应的体材料.根据X射线衍射谱确定所得纳米和体材料样品均为纯立方相.实验表明在纳米尺寸样品中随着Ag离子浓度的增加，荧光发射强度随之增加，当X=2×10^-2时达到最大值，其发光强度比X=0时提高了近50%.当Ag离子浓度继续增加，样品发光强度保持不变.在相应的体材料样品中则没有观察到此现象.通过对各样品的发射光谱，激发光谱，X射线衍射图谱，透射电镜(TEM)照片和荧光衰减曲线的研究，分析了引起纳米样品荧光强度变化的原因是由于Ag离子与表面悬键氧结合，从而使这一无辐射通道阻断，使发光中心Eu³⁺的量子效率提高；Ag⁺的引入所带来的另一个效应是使激发更为有效.这两方面原因使发光效率得到了提高.     

Down-conversion near infrared emission in Pr, Yb co-doped Y2O3 transparent ceramics

Pr³⁺, Yb³⁺ co-doped Y₂O₃ transparent ceramics have been prepared by the solid state reaction and vacuum sintering. Down-conversion near infrared emission has been demonstrated upon a 482 nm excitation. The energy of the 482 nm blue photon was first absorbed by Pr³⁺ and then delivered to Yb³⁺. Possible energy transfer mechanisms from Pr³⁺ to Yb³⁺ have been discussed. Under the 482 nm excitation, the Pr⁴⁺-Yb²⁺ charge transfer state would not seriously influence the energy transfer process. The dominant one should be either the cooperative down-conversion or the two-step photon emission. The efficient down-conversion near infrared emission has potential application in enhancing the conversion efficiency of crystalline silicon solar cells.     

Vaaisible upconversion emission of Er3+-doped and Er3+/Yb3+-codoped LiInO2

Lithium-indium oxide is a high-density (5.9 g·cm⁻³), wide band-gap semiconductor with promising applications for scintillating detection of solar neutrinos as well as for efficient phosphorescence when doped with Er³⁺ or Sm³⁺ ions. In this report, we demonstrate visible upconversion emission of Er³⁺-doped LiInO₂ synthesized by a simple solid-state chemistry procedure and discuss mechanisms responsible for pumping the Er³⁺ ions to upper levels. Intense upconversion emission is observed in the green and red spectral regions under near-infrared excitation, and it is greatly enhanced by co-doping with Yb³⁺ ions. We also examined the upconversion intensity change as a function of temperature, and, consequently, possible applications of this material as a low-temperature sensor.     

CW infrared laseraction of optically pumped Co2+:KZnF3

The optical properties of KZnF₃:Co²⁺ were investigated by means of absorption and emission spectroscopy in the visible and infrared spectral region. This system is suitable for laseraction between the lowest ⁴T₁(⁴F)-⁴T₂(⁴F) Co²⁺ phonon sidebands. CW laseraction of more than 20 mW (85K) was observed at 1.95 μm when pumped with an Ar⁺-laser at 514 μm (1.5W). The system is at least tunable between 2.05 μm to 1.85 μm.     

ESR of Fe3+ -Rhombic,Fe2+ -Vo and Fe1+ -Vo complexes in SrTiO3

Three new Fe-defect complexes have been identified by ESR in Fe doped crystals of SrTiO₃. These are an Fe³⁺ center with rhombic fine structure in the “as-grown” crystals, and the vacancy associated complexes Fe²⁺ -V_o and Fe¹⁺ -V_o in “reduced” crystals. Photo-excited charge transfer effects are observed for these centers.     

Enhanced white light emission in Er/Tm/Yb/Li codoped Y2O3 nanocrystals

Er/Tm/Yb codoped Y₂O₃ nanocrystals and Er/Tm/Yb/Li codoped Y₂O₃ nanocrystals have been synthesized by sol-gel method, bright white light emission has been observed at 976 nm excitation. The blue, green, and red emissions, respectively, arise from the transitions ¹G₄ → ³H₆ of Tm³⁺, ²H_11/2/⁴S_3/2 → ⁴I_15/2, and ⁴F_9/2 → ⁴I_15/2 of Er³⁺ ion. Moreover, after doping Li⁺ ions into Er/Tm/Yb codoped Y₂O₃ nanocrystals, the white light emission increase greatly. CIE coordinate of Er/Tm/Yb/Li codoped Y₂O₃ nanocrystals is X = 0.32 and Y = 0.36 at 10 W/cm² excitation, which is very close to the standard equal energy white light illuminate (X = 0.33, Y = 0.33).     

Single-crystal absorption and emission spectra of CsVCl3 and CsMgCl3:V2+

Single-crystal absorption and emission spectra of CsVCl₃ and CsMgCl₃:V²⁺ in the region of the first excited state were measured at temperatures down to 6 K. The ⁴A_2g?⁴T_2g transition shows a large trigonal splitting of the ⁴T_2g state and surprisingly well-resolved fine structure which can be analyzed in terms of electronic origins and vibronic side bands.     

Investigation of emission properties of Tm3＋：Y2O3 transparent ceramic

A transparent and emitting ceramic of Y 2 O 3 doped with 6% Tm 3+ ions is fabricated by vacuum sintering with ZrO 2 . Absorption, photoluminescence (PL), and PL excitation (PLE) spectra are investigated in a spectral range of 200 to 2 100 nm at various temperatures between 296 and 12 K. Intense emission band appears at 450 to 465 nm in the visible range. Near-infrared emission bands are observed at 1 200 to 1 300 nm and 1 400 to 1 550 nm, with intense peaks at 1 270, 1 450, and 1 523 nm. The luminescence mechanisms and potential applications of the emissions are discussed with the help of Judd-Ofelt theory and PLE spectra.     

Ni^2＋：LiNbO3的光学吸收谱和EPR的研究

应用三角晶场中d^2(d^8)电子组态的包括静电相互作用和自旋－轨道耦合相综合利用物强场能量矩阵,采用完全对角化方法,精确地计算了具有C3V对称的Ni^2 :LiNbO3的光学吸收谱和EPR谱。理论结果与实验值符合得很好。     

Ba2+掺杂钙钛矿Bi0.5Ca0.5MnO3多晶材料的结构、磁性和输运性质研究

本文系统地研究了具有电荷有序(CO)和C型反铁磁(AFM)磁结构的钙钛矿锰氧化物Bi0.5Ca0.5-xBaxMnO3(x=0,0.03,0.05,0.07 and 0.10)的结构、磁性和电输运性质.系统晶格对称性保持Pnma空间群正交结构不变.随着Ba掺杂浓度的提高,电荷有序转变温度和反铁磁转变温度明显降低,表明掺...