Morphology-dependent luminescence behavior of Y<Subscript>2-x</Subscript>Gd<Subscript>x</Subscript>O<Subscript>3</Subscript>:Eu<Superscript>3+</Superscript> thin-film phosphors grown by a laser ablation

Y_2-xGd_xO₃:Eu³⁺ luminescent thin films have been grown on Al₂O₃(0001) substrates using pulsed laser deposition. Films grown under different deposition conditions have been characterized using microstructural and luminescence measurements. The crystallinity, surface morphology and photoluminescence (PL) of the films are highly dependent on the amount of Gd present. The photoluminescence (PL) brightness data obtained from Y_2-xGd_xO₃:Eu³⁺ films grown under optimized conditions have indicated that Al₂O₃(0001) is one of the most promising substrates for the growth of high-quality Y_2-xGd_xO₃:Eu³⁺ thin-film red phosphors. In particular, the incorporation of Gd into the Y₂O₃ lattice could induce a remarkable increase of PL. The highest emission intensity was observed with Y_1.35Gd_0.60Eu_0.05O₃, whose brightness was increased by a factor of 3.1 in comparison with that of Y₂O₃:Eu³⁺ films. This phosphor may be promising for application in flat-panel displays. PACS 78.20.-e; 78.55.-m; 78.66.-w     

Improved photoluminescence of pulsed-laser-ablated Y<Subscript>1-x</Subscript>Gd<Subscript>x</Subscript>VO<Subscript>4</Subscript>:Eu<Superscript>3+</Superscript> thin film phosphors by Gd substitution

Gd-substituted Y_1-xGd_xVO₄:Eu³⁺ luminescent thin films have been grown on Al₂O₃(0001) substrates using pulsed-laser deposition. The films grown under different deposition conditions have been characterized using microstructural and luminescent measurements. The crystallinity, surface morphology, and photoluminescence (PL) of the films are highly dependent on the amount of Gd. The photoluminescence (PL) brightness data obtained from Y_1-xGd_xVO₄:Eu³⁺ films grown under optimized conditions have indicated that the PL brightness is more dependent on the surface roughness than the crystallinity of the films. In particular, the incorporation of Gd into the YVO₄ lattice could induce a remarkable increase of PL. The highest emission intensity was observed with Y_0.57Gd_0.40Eu_0.03VO₄ thin film whose brightness was increased by a factor of 2.5 and 1.9 in comparison with that of YVO₄:Eu³⁺ and GdVO₄:Eu³⁺ films, respectively. This phosphor have application to flat panel displays. PACS 78.20.-e; 78.55.-m; 78.66.-w     

GdxY1-xCa4O(BO3)3晶体非临界相位匹配波长的研究

根据YCa₄O(BO₃)₃(YCOB),GdCa₄O(BO₃)₃(GdCOB)的折射率拟合方程,分析了Gd_xY_1-xCOB可实现非临界相位匹配的波长范围.利用704-5型光参量放大器,测量了非临界相位匹配波长随组分x的变化关系. 关键词： xY_1-xCOB晶体')" href="#">Gd_xY_1-xCOB晶体 非临界相位匹配波长     

Crystallinity and morphology dependent luminescence of Li-doped Y2−xGdxO3:Eu thin film phosphors

The influence of lithium doping on the crystallization, the surface morphology, and the luminescent properties of pulsed laser deposited Y_2−xGd_xO₃:Eu³⁺ thin film phosphors was investigated. The crystallinity, the surface morphology, and the photoluminescence (PL) of films depended highly on the Li-doping and the Gd content. The relationship between the crystalline and morphological structures and the luminescent properties was studied, and Li⁺ doping was found to effectively enhance not only the crystallinity but also the luminescent brightness of Y_2−xGd_xO₃:Eu³⁺ thin films. In particular, the incorporation of Li and Gd into the Y₂O₃ lattice could induce remarkable increase in the PL. The highest emission intensity was observed Li-doped Y_1.35Gd_0.6O₃:Eu³⁺ thin films whose brightness was increased by a factor of 4.6 in comparison with that of Li-doped Y₂O₃:Eu³⁺ thin films.     

Patterning and morphology of nonlinear optical Gd<Subscript>x</Subscript>Bi<Subscript>1-x</Subscript>BO<Subscript>3</Subscript> crystals in CuO-doped glass by YAG laser irradiation

Dots and lines consisting of nonlinear optical Gd_xBi_1-xBO₃ crystals were patterned on the surface of CuO-doped Gd₂O₃-Bi₂O₃-B₂O₃ glass by heat-assisted (200 °C) Nd:YAG laser irradiations with a wavelength of λ=1064 nm, where the laser energy absorbed by Cu²⁺ is converted to the local heating of the surrounding Cu²⁺. The surface morphology and orientation of crystals in the patterned lines were clarified from confocal scanning laser microscope observations and polarized micro-Raman scattering spectra. Crystal lines with periodic bumps (i.e., ladder-shape like lines) were patterned by laser irradiations with a power of 0.79 W and a scanning speed of 60 μm/s, and the orientation of Gd_xBi_1-xBO₃ crystals in the lines was proposed. The present study demonstrates that the combination of Cu²⁺ and continuous wave Nd:YAG laser with λ=1064 nm is effective in inducting crystallization of oxide glasses. The mechanism of laser-induced crystallization in glass has also been discussed. PACS 61.43.Fs; 42.70.Mp; 68.35.Bs; 78.30.-j; 79.20.Ds     

Gd3Al2-xGax合金的磁熵研究

用磁控电弧炉在氩气气氛中熔炼了Gd₃Al_2-xGax(x=0,0.1,0.3,0.5)系列合金.通过X射线粉末衍射和振动样品磁强计研究了样品的结构和磁熵.发现样品都是由Zr₃Al₂相组成的,且GdAlGa系列合金的ΔS_m要比Gd₃Al₂的大,峰值在室温附近,温区较宽,是一种较好的磁致冷材料. 关键词：     

3∶29型Gd3(Fe1-xCox)29-yCry化合物的成相与结构

通过X射线衍射分析和磁测量研究了Gd-Fe-Co-Cr四元系中对应于化学式Gd₃(Fe,Co,Cr)₂₉且Gd含量为一定值的截面内富Fe,Co区的相关系,重点探索了高Co含量3∶29型化合物合成的可能性,研究了3∶29型Gd₃(Fe_1-xCo_x)_29-yCr_y化合物的结构与磁性.研究结果表明,获得3∶29型单相Gd₃(Fe_1-xCo_x)_29-yCr_y化合物的范围为:y=5,0≤x≤0.7;y=5.5,0.7≤x≤0.8和y=6,0.8≤x≤0.9.基于对Gd₃(Fe_1-xCo_x)_29-yCr_y化合物成相条件的研究,成功地合成了纯Co基Gd₃Co_29-yCr_y化合物,其固溶范围为6.5≤y≤7.3.3∶29型单相Gd₃(Fe_1-xCo_x)_29-yCr_y化合物的晶体结构都属于单斜晶系,Nd₃(Fe,Ti)₂₉型结构,空间群为A2m.得到3∶29型单相Gd₃(Fe_1-xCo_x)_29-yCr_y化合物的固溶极限即Co含量的极大值与稳定元素Cr含量有关.Co原子的含量越高,所需稳定元素Cr的含量越大.值得注意的是,用Co原子替代Fe原子会导致Gd₃(Fe_1-xCo_x)_29-yCr_y化合物磁晶各向异性的显著改变.当x≥0.4时,化合物的磁晶各向异性从易面型转变为易轴型 关键词： 3(Fe_1-xCo_x)_29-yCr_y化合物')" href="#">Gd₃(Fe_1-xCo_x)_29-yCr_y化合物 相关系和相结构 X射线衍射 磁晶各向异性     

Non-critical phase-matched second harmonic generation in Gd<Subscript>x</Subscript>Y<Subscript>1-x</Subscript>COB

We have characterized non-critical phase-matching (NCPM) for both Type I and Type II second harmonic generation (SHG) in y-cut Gd_xY_1-xCOB using a nanosecond optical parametric oscillator (OPO). The variation of the NCPM wavelength with temperature was investigated for different values of the compositional parameter x. Efficient SHG of 1064 nm was achieved by choosing the suitable compositional parameter x=0.28 and by tuning the temperature of the crystal to 52 °C. Using a 25-mm-long Gd_0.28Y_0.72COB crystal, conversion efficiencies of 41 and 43% were obtained respectively from a mode-locked Nd:YAG and a Q-switched Nd:YAG laser. PACS 42.25.Lc; 42.65.Ky; 42.70.Mp; 42.79.Nv     

UV excitable Y2? x ? y Gd y SiO5:Ce x phosphors for cool white light emission

Cool white light was realized in Y_2−x−y Gd _x SiO₅: Ce _y phosphor under near UV excitation, due to the occupation Ce³⁺ in Y³⁺ 1st and 2nd site, synthesized using solid state carbothermal reduction route. SEM with elemental analysis show the existence of Gd in Y₂SiO₅:Ce enhances the particles size in comparison to Y₂SiO₅:Ce phosphors alone. Gd³⁺ (0.00≤x≤0.75) and Ce³⁺ (0.02≤y≤0.10) concentration was optimized to 0.50 and 0.08 in Y₂SiO₅, respectively. The CIE chromaticity color coordinates (0.24, 0.20) are close to cool white light value which could be useful for the fabrication of cool white LED.     

3:29型Gd-Fe-Co-Cr化合物的结构和磁性

制备了Gd₃(Fe_1-xCo_x)₂₅Cr₄(0≤x≤0.6)和Gd₃Fe_29-yCr_y(3.5≤x≤5.0)化合物,通过X射线衍射和磁性测量手段研究了它们的结构和磁性.实验表明这些化合物都属于A_2/m空间群.Cr含量增加导致居里温度下降,饱和磁化强度降低,磁晶各向异性场下降.Co替代Fe导致单胞体积收缩,居里温度升高,5K的饱和磁化强度在x=0.3左右达到极大值,磁晶各向异性在x=0.4附近由易面转变为易轴. 关键词：     

Spin-wave excitations in finite chain segments of the diluted one-dimensional Heisenberg antiferromagnet CsM{n_{1 - x}}M{g_x}B{r_3}

The inelastic neutron scattering technique was employed to study the magnetic excitation spectra in the diluted one-dimensional Heisenberg antiferromagnet CsMn_1-xMg_xBr₃ (x =0, 0.05, 0.10, 0.25, 0.50). The spectral response is interpreted in terms of spin-wave excitations in finite chain segments of Mn²⁺ ions, which are found to exist as long as the chain length exceeds twice the wavelength of the spin excitation. This limit determines the crossover into the mesoscopic regime. Received 31 December 1999     

Y1-xCaxBa2Cu3-xMxO7-δ (M=Fe,Ni)体系的超导电性

本文报道,通过对Y_1-xCa_xBa₂Cu_3-xMxO_7-δ(M=Fe,Ni)体系样品的晶体结构、氧含量、正常态电阻率与温度的关系,以及超导转变温度等测量,并与YBa₂Cu_3-xMxO_7-δ(M=Fe,Ni)体系进行比较,发现Y_1-xCa_xBa₂Cu_3-xFe_xO_7-δ体系的T_c显著地高于相应x值的YBa₂Cu_3-xFe_xO_7-δ体系,而Y_1-xCa_xBa₂Cu_3-xNi_xO_7-δ体系则相反,T_c低于仅Ni替代的体系,表明Ca和Fe同时替代时两者引起的载流子浓度(n_H)变化相互补偿,抑制了仅Fe替代时引起的n_H和T_c急剧下降;而作Ca和Ni同时替代时主要的不是两者引起载流子浓度变化的相互补偿,Ca和Ni替代效应之间的关联较弱。作者认为,对Y_1-xCa_xBa₂Cu_3-xFe_xO_7-δ体系属于CuO₂平面外的元素替代,这时载流子浓度是决定Tc的主要因素;而对Y_1-xCa_xBa₂Cu_3-xNi_xO_7-δ体系,由于Ni²⁺离子主要占据Cu(Ⅱ)位,它导致磁拆对效应,Ni²⁺离子的拆对效应是引起T_c下降的直接原因。 关键词：     

Study of the magnetic phase diagram of Y1-x Cax Ba2 Cu3 O6

We have studied the magnetic phase diagram for the bilayer compound Y_1-x Ca_x Ba₂ Cu₃ O₆ in the regime of low doping (hole concentration within a CuO₂ plane, p_sh < 0.1). For p_sh < 0.03, the data demonstrate the freezing of the spin degrees of freedom associated with the doped holes into a spin‐glass‐like state which is superimposed on the preexisting long range order of the Cu²⁺ spins. Only a single spin‐glass like transition at a temperature T_g is observed for samples in the hole concentration range 0.03 < p_sh < 0.1. While the threshold for the occurrence of superconductivity is almost the same (p_sh > 0.06) for the Y_1-x Ca_x Ba₂ Cu₃ O₆ and the La_2-x Sr_x CuO₄ systems, the magnetic correlations that coexist with superconductivity are considerably stronger in the bilayer Y_1-x Ca_x Ba₂ Cu₃ O₆ system as indicated by significantly increased transition temperatures T_g. This revised version was published online in August 2006 with corrections to the Cover Date.     

Low-voltage cathodoluminescence property of Li-doped Gd2−xYxO3:Eu

Cathodoluminescent (CL) spectra of Li-doped Gd_2−xY_xO₃:Eu³⁺ solid-solution (0.0?x?0.8) were investigated at low voltages (300 V-1 kV). The CL intensity is maximum for the composition of x=0.2 and gradually reduces with increasing the amount of substituted Y content. In particular, small (∼100 nm) particles of Li-doped Gd_1.8Y_0.2O₃:Eu³⁺ are obtained by firing the citrate precursors at only 650°C for 18 h. Relative red-emission intensity at 300 V of this phosphor is close to 180% in comparison with that of commercial red phosphor Y₂O₃:Eu³⁺. An increase of firing temperature to 900°C results in 400-600 nm sized spherical particles. At low voltages (300-800 V), the CL emission of 100 nm sized particles is much stronger than that of 400-600 nm sized ones. In contrast, the larger particles exhibit the higher CL emission intensity at high voltages (1-10 kV). Taking into consideration small spherical morphology and effective CL emission, Li-doped Gd_1.8Y_0.2O₃:Eu³⁺ appears to be an efficient phosphor material for low voltage field emission display.     

Electronic structure and magnetic properties of BaTi1-xMnxO3

The electronic structure and magnetic properties of polycrystalline BaTi_1-xMn_xO₃ (x = 0–0.1) compounds prepared by solid-state reactions were studied. The results revealed that the increase in Mn content (x) did not change the oxidation numbers of Ba (+2) and Ti (+4) in BaTi_1-xMn_xO₃. However, there is the change in Mn valence that Mn^3+,4+ ions coexist in the samples with x = 0.01–0.04 while Mn⁴⁺ ions are almost dominant in the samples with x = 0.06–0.1. We also point out that Mn³⁺ and Mn⁴⁺ ions substitute for Ti⁴⁺ and prefer locating in the tetragonal and hexagonal BaTiO₃ structures, respectively, in which the hexagonal phase constitutes soon as x = 0.01. Particularly, all the samples exhibit room-temperature ferromagnetism. Ferromagnetic order increases with increasing x from 0 to 0.02, but decreases as x ≥ 0.04. We think that ferromagnetism in BaTi_1-xMn_xO₃ is related to lattice defects and/or exchange interactions between Mn³⁺ and Mn⁴⁺ ions.     

Electrical properties of heavily doped fluorite-structured BaF2:RF3 (R=La, Pr, Nd, Gd, Tb, Y, Sc) single crystals

The superionic conductivity and dielectric response of heavily doped fluorite-structured Ba_1−xR_xF_2+x (R=La, Pr, Nd, Gd, Tb, Y, Sc; x=0.005–0.45) crystals are reported. The highest ionic conductivity is found for R=Sc and x=0.1. Upon ScF₃ doping, small Sc³⁺ ions rearrange their surroundings, create excessive fluoride interstitial ions and bring about a high ionic conductivity. For each dopant, the concentration dependence of the ionic conductivity is non-linear. A monotonous concentration dependence of the ionic conductivity is found only for La³⁺ doping. Upon doping with Nd³⁺, Gd³⁺, Tb³⁺, Y³⁺ and Sc³⁺ ions, a conductivity maximum is observed at x=0.1–0.2. Upon Pr³⁺ doping, this maximum is split. The influence of defect clustering on the concentration dependence of the conductivity is discussed. Paper presented at the 6th Euroconference on Solid State Ionics, Cetraro, Calabria, Italy, Sept. 12–19, 1999.     

Synthesis and properties of In2(Se1-xTex)3 thin films: a new semiconductor compound

In₂(Se_1-xTe_x)₃ polycrystalline films were prepared by a dual-source thermal evaporation technique. The depositions onto glass and SnO₂-coated glass substrates were carried out in a vacuum chamber and followed by an annealing in neutral ambient (Ar or N₂). The structural, morphological and compositional studies of the films were made by X-ray diffraction, energy-dispersive X-ray analysis, X-ray photoelectron spectroscopy, scanning electron microscopy, Raman scattering and optical transmission. Optimum conditions are investigated for the formation of the ternary compound In₂(Se_1-xTe_x)₃ in order to tune the band gap by changing the Te concentration. The film properties as a function of Te amount are discussed. It is shown that single-phase, textured and homogeneous layers of In₂(Se_1-xTe_x)₃ can be grown with x≤0.2 at optimal deposition and heat treatment conditions. For x≅0.17 these films showed an energy band gap of about 1.45 eV and an electrical conductivity at room temperature six orders of magnitude higher than that of the binary γ-In₂Se₃ thin films. Received: 9 July 1999 / Accepted: 25 November 1999 / Published online: 13 July 2000     

Electro-optic properties of LiKSO4 and LiK1-xRbxSO4 crystals

1-x Rb_xSO₄ for x varying between 0 and 0.50 were investigated by an ac modulation method based upon the Sénarmont arrangement. The electro-optic coefficient r_c, and for the first time the coefficients r₄₁ and r₅₁ were determined with good accuracy in pure LiKSO₄ around room temperature at a wavelength of 633 nm. The frequency dependence of the electro-optic coefficient r_c was measured in the frequency range from 1 kHz up to 1 MHz. The values of the factor of merit n_e ³r_c of the mixed crystals LiK_1-xRb_xSO₄ were obtained for the first time, for the concentrations x=0.05, 0.10, 0.20, and 0.50. The electro-optic properties are shown to be affected by the random presence of the rubidium ions in this disordered system. Received: 16 March 1998/Revised version: 2 June 1998     

(Nd1－xGdx)3Fe27.31Ti1.69化合物的结构和磁性

通过X射线衍射和磁性测量等手段研究了(Nd_1-xGd_x)₃Fe_27.31Ti_1.69(0≤x≤0.6)化合物的结构和磁性.X射线衍射测量结果表明Gd替代后并未改变Nd₃(Fe,Ti)₂₉化合物的晶体结构，但引起了晶胞体积收缩.随着Gd含量的增加，化合物的居里温度T_C和室温磁晶各向异性场B_a单调增加，而自旋重取向 关键词： 1-xGd_x)₃Fe_27.31Ti_1.69化合物')" href="#">(Nd_1-xGd_x)₃Fe_27.31Ti_1.69化合物 磁晶各向异性 自旋重取向 磁相图     

用脉冲激光方法在Si(100)上沉积的Cox-C1-x颗粒膜及其磁电阻效 应

利用脉冲激光沉积方法在Si(100)上制备了Co_x-C_1-x颗粒膜，并研 究了其正磁电阻 效应.实验结果表明，样品在室温下的正磁电阻效应要远远高于低温下的正磁电阻效应；Co _0.02-C_0.98样品具有最大的室温正磁电阻效应，在外加磁场B=1T时 ，其磁电阻 率MR=22%；随着Co含量的增加，Co_x-C_1-x颗粒膜的正磁电阻效应呈 减小趋势.样品 的MR-B的曲线与传统的多 关键词： 正磁电阻效应 x-C_1-x颗粒膜')" href="#">Co_x-C_1-x颗粒膜 脉冲激光沉积