共查询到20条相似文献,搜索用时 93 毫秒
1.
Kwang-Bok Kim Kyung-Wan Koo Tong-Yul Cho Hui-Gon Chun 《Materials Chemistry and Physics》2003,80(3):682-689
The blue phosphor of BaMgAl10O17:Eu2+ (BAM) powders were prepared by solid-state reaction. The thermal degradation of BAM phosphor significantly reduces the intensity of the blue emission. BAM is reduced by an amount of 50% after heating at around 800 °C for 1 h. Photoluminescence (PL) excitation and emission spectra showed that the blue emission of 450 nm peak decreased with increasing annealing temperature. The 5D0→7F1 and 5D0→7F2 transition of Eu3+ were observed at 590 and 615 nm emission lines over 1100 °C. Electron paramagnetic resonance (EPR) spectrum also detected two signals of Eu2+, corresponding to g=3.7156(9) for 88 mT, and g=2.9507(9) for 133 mT. X-ray absorption near edge structure (XANES) spectrum decreased the intensity of Eu2+ for 6977 eV with increasing annealing temperature, while high-energy peak of Eu3+ for 6984 eV was increased. The combined use of X-ray and neutron data by the Rietveld refinement appears to support that the secondary phase of EuMgAl11O19 magnetoplumbite structure in BAM may be formed by heat treatment. 相似文献
2.
This paper reports the preparation process and the long lasting phosphorescence of the Sr4Al14O25:Eu2+,Dy3+ thin films obtained by magnetron sputtering. Phosphorescence was achieved by annealing the films in reducing atmosphere. Sr4Al14O25 thin film was obtained when the films were treated at 1200 °C, while SrAl2O4 was generated as the intermediate phase during the annealing process. Sr4Al14O25:Eu2+,Dy3+ film generated an emission at 485 nm, and SrAl2O4:Eu2+,Dy3+ film showed an emission peaking at 515 nm. Afterglow characteristics were observed for both films, and Sr4Al14O25:Eu2+,Dy3+ film showed a better afterglow property than the SrAl2O4:Eu2+,Dy3+ film due to a deeper trap level and a higher trap concentration formed in the thin films. 相似文献
3.
The synthesis and photoluminescent (PL) properties of calcium stannate crystals doped with europium grown by mechanically activated in a high energy vibro-mill have been investigated. The characteristics of Ca2SnO4:Eu3+ phosphors were found to depend on the amounts of europium ions. The XRD profiles revealed that the system, (Ca1−xEux)2SnO4, could form stable solid solutions in the composition range of x = 0–7% after being calcined at 1200 °C. The calcined powders emit bright red luminescence centered at 618 nm due to 5D0 → 7F2 electric dipole transition. Both XRD data and the emission ratio of (5D0 → 7F2)/(5D0 → 7F1) reveal that the site symmetry of Eu3+ ions decreases with increasing doping concentration. The maximum PL intensity has been obtained for 7 mol% concentration of Eu3+ in Ca2SnO4. 相似文献
4.
Roberval Stefani Alessandra de S. Maia Cludia A. Kodaira Ercules E.S. Teotonio Maria C.F.C. Felinto Hermi F. Brito 《Optical Materials》2007,29(12):1852-1855
Eu2+ ion doped into SrB4O7 matrix was prepared by combustion method heated at 900 °C in air, using urea (U) or glycine (G) as fuels in different ratios (U100, A10, A25, G10, G25, G75, and G100). In some compositions, ammonium acetate (AA) was used to reduce the exothermicity of combustion reaction. X-ray diffraction and luminescence spectroscopy were used to characterize the material. The high intense emission band at 367 nm is assigned to 4f65d → 4f7(8S7/2) transition arisen from divalent europium ion. It is observed that the interconfigurational transition is dependent on the molar ratio of glycine:urea fuels. Glycine fuel favors Eu2+ formation in SrB4O7 host lattice prepared by combustion method. 相似文献
5.
It has been found that charge compensated CaMoO4:Eu3+ phosphors show greatly enhanced red emission under 393 and 467 nm-excitation, compared with CaMoO4:Eu3+ without charge compensation. Two approaches to charge compensation, (a) 2Ca2+ → Eu3+ + M+, where M+ is a monovalent cation like Li+, Na+ and K+ acting as a charge compensator; (b) 3Ca2+ → 2Eu3+ + vacancy, are investigated. The influence of sintering temperature and Eu3+ concentration on the luminescent property of phosphor samples is also discussed. 相似文献
6.
Bi2O3·B2O3 glasses doped with rare-earth oxides (RE2O3) (RE3+ = La3+, Pr3+, Sm3+, Gd3+, Er3+ and Yb3+) were prepared by the melting–quenching method. The relationships between composition and properties were demonstrated by IR, DSC, XRD and SEM analysis. The results show that the network structure resembles that of undoped Bi2O3·B2O3 glass, composing of [BO3], [BO4] and [BiO6] units. RE2O3 stabilizes the glass structure as a modifier. Transition temperature (Tg) increases linearly with cationic field strength (CFS) of RE3+. La2O3, Pr2O3, Sm2O3 and Gd2O3 are benefit to promote the formation of BiBO3 crystal. When Er2O3 and Yb2O3 are introduced, respectively, the main crystal phase changes to Bi6B10O24. Transparent surface crystallized samples are obtained by reheating at 460–540 °C for 5 h. In this case, needle like BiBO3 crystal or rare-earth-doped BiBO3 crystal (PrxBi1−xBO3 and GdxBi1−xBO3) are observed, which is promising for non-linear optical application. 相似文献
7.
Nobuko Maeda Noriyuki Wada Hiroaki Onoda Akira Maegawa Kazuo Kojima 《Optical Materials》2005,27(12):1851-1858
Thin films of the system xAl2O3–(100 − x)Ta2O5–1Er2O3 were prepared by a sol–gel method and a dip-coating technique. The influences of the composition and the crystallization of the films on Er3+ optical properties were investigated. Results of X-ray diffraction indicated that the crystallization temperature of Ta2O5 increased from 800 to 1000 °C with increased values of x. In crystallized films, the intensities of the visible fluorescence and upconversion fluorescence tend to decrease with an increase in x values, due to the high phonon energy of Al2O3; the strongest fluorescence is observed in a crystallized film for x = 4 heat treated at 1000 °C. In amorphous films obtained by heat treatment at relatively low temperatures the Er3+ fluorescence could not be observed because strong fluorescence from organic residues remaining in the films thoroughly covered the Er3+ fluorescence. On the other hand, the Er3+ upconversion fluorescence in the amorphous films was observed to be stronger than that in the crystallized films. The strongest upconversion fluorescence is observed in an amorphous film for x = 75 heat treated at 800 °C. 相似文献
8.
Nanocrystalline Gd2O3:A (A=Eu3+, Dy3+, Sm3+, Er3+) phosphor films and their patterning were fabricated by a Pechini sol–gel process combined with a soft lithography. X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM) and optical microscopy, UV/vis transmission and photoluminescence (PL) spectra as well as lifetimes were used to characterize the resulting films. The results of XRD indicated that the films began to crystallize at 500 °C and that the crystallinity increased with the elevation of annealing temperatures. Uniform and crack free non-patterned phosphor films were obtained by optimizing the composition of the coating sol, which mainly consisted of grains with an average size of 70 nm and a thickness of 550 nm. Using micro-molding in capillaries technique, we obtained homogeneous and defects-free patterned gel and crystalline phosphor films with different stripe widths (5, 10, 20 and 50 μm). Significant shrinkage (50%) was observed in the patterned films during the heat treatment process. The doped rare earth ions (A) showed their characteristic emission in crystalline Gd2O3 phosphor films due to an efficient energy transfer from Gd2O3 host to them. Both the lifetimes and PL intensity of the rare earth ions increased with increasing the annealing temperature from 500 to 900 °C, and the optimum concentrations for Eu3+, Dy3+, Sm3+, Er3+ were determined to be 5, 0.25, 1 and 1.5 mol% of Gd3+ in Gd2O3 films, respectively. 相似文献
9.
β-Ga2O3晶体是一种新型宽禁带氧化物半导体材料, 本征导电性差。为了在调控导电性能的同时兼顾高的透过率和结晶性能, 离子掺杂是一种有效的途径。采用光学浮区法生长出ϕ8 mm×50 mm蓝色透明In:Ga2O3晶体, 晶体具有较高的结晶完整性。In3+离子掺杂后, β-Ga2O3晶体在红外波段出现明显的自由载流子吸收, 热导率稍有减小。室温下, In:Ga2O3晶体的电导率和载流子浓度分别为4.94×10-4 S/cm和1.005×1016 cm-3, 其值高于β-Ga2O3晶体约1个数量级。In:Ga2O3晶体电学性能对热处理敏感, 1200℃空气气氛和氩气气氛退火后电导率降低。结果表明, In3+离子掺杂能够调控β-Ga2O3晶体的导电性能。 相似文献
10.
Absorption and emission spectra of Eu and Dy, Yb and Ti ions in Li2B4O7 glasses grown in oxygen and hydrogen gas atmospheres were measured for valency states and lattice-sites analysis. For the Li2B4O7 glass doped with Eu2+, Eu3+ and Dy3+ ions which were grown in oxidizing and reducing atmospheres, absorption and emission bands due to these ions were investigated before and after γ-irradiation. For the Yb3+-doped Li2B4O7 glass, a weak, broad band was observed near the sharp 976.3 nm absorption band. The origin of this band is discussed in comparison with other glasses. Moreover, irradiation experiments using γ-rays were also performed in order to investigate the possibility of valency change of Yb ions. It was found that Ti4+ ions, which are produced under oxidizing atmosphere, change to Ti3+ ions after γ-irradiation with a dose of 105 Gy. An additional absorption band observed at about 500 nm is due to the Ti3+ ions accompanied by charge-compensating vacancy and does not give any emission. 相似文献
11.
Nanosized strontium aluminate phosphors co-activated by Eu2+ and Dy3+ were prepared via a novel reverse microemulsion process. This new synthesis technique lowered the synthesis temperature of SrAl2O4: Eu2+, Dy3+ phosphors to as low as 900 °C, and also reduced the particle size to the nanometer scale (around 40 nm). In the microemulsion process, the constituent cations were trapped by numerous nano-scaled micelles, leading to a shortening of the inter-diffusion length and enhancement of the precursor reactivity. The excitation intensity and emission peaks of nanosized SrAl2O4: Eu2+, Dy3+ phosphors significantly increased with increasing heating temperatures. 相似文献
12.
Qi Song Cheng-Ren Li Jian-Yong Li Wan-Yu Ding Shu-Feng Li Jun Xu Xin-Lu Deng Chang-Lie Song 《Optical Materials》2006,28(12):1344-1349
The Yb:Er co-doped Al2O3 thin film was deposited on oxidized silicon wafers by microwave ECR plasma source enhanced RF magnetron sputtering, and annealed from 800 °C to 1000 °C. The photoluminescence at 1.53 μm of thin film was obtained under room temperature. The mixture phase structure of γ and θ is observed by XRD, and the compositions of the thin film are investigated by EPMA. The maximum PL intensity was achieved with O2:Ar at 1:1, annealing temperature at 900 °C, and experimental ratio of Yb:Er at 1:3.6. The energy transfer mechanism between Er and Yb ions is supported by theoretical analysis and experiment results. 相似文献
13.
The microstructure, electrical properties, dielectric characteristics, and DC-accelerated aging behavior of the ZnO–V2O5–MnO2 system sintered were investigated for MnO2 content of 0.0–2.0 mol% by sintering at 900 °C. For all samples, the microstructure of the ZnO–V2O5–MnO2 system consisted of mainly ZnO grain and secondary phase Zn3(VO4)2. The incorporation of MnO2 to the ZnO–V2O5 system was found to restrict the abnormal grain growth of ZnO. The nonlinear properties and stability against DC-accelerated aging stress improved with the increase of MnO2 content. The ZnO–V2O5–MnO2 system added with MnO2 content of 2.0 mol% exhibited not only a high nonlinearity, in which the nonlinear coefficient is 27.2 and the leakage current density is 0.17 mA/cm2, but also a good stability, in which %ΔE1 mA = −0.6%, %Δ = −26.1%, and %Δtan δ = +22% for DC-accelerated aging stress of 0.85E1 mA/85 °C/24 h. 相似文献
14.
Zhihua Xu Yongxiang Li Zhifu Liu Zhi Xiong 《Materials Science and Engineering: B》2004,110(3):302-306
The synthesis of trivalent terbium doped ZnGa2O4 nanosized new phosphors by the Pechini method was reported. Well-crystallized ZnGa2O4:Tb3+ phosphors were obtained at low-temperature about 550 °C. The phosphors formed porous agglomerates which consist of spherical nanocrystallites with a uniform size at about 30 nm. The photoluminescence of the phosphors included both the luminescence of ZnGa2O4 host and characteristic emission of Tb3+, and the excitation spectra showed an energy transfer from the host lattice to the activator. The Tb3+ emission from the phosphors prepared by the Pechini process was more intensive than that of phosphors by solid-state reaction process. 相似文献
15.
Haiping Zhang Mengkai Lü Zhiliang Xiu Guangjun Zhou Shufen Wang Yuanyuan Zhou Shumei Wang 《Materials Science and Engineering: B》2006,130(1-3):151-157
Single-phase YVO4:Eu3+ nanopowders were synthesized by sol–gel combustion method using citric acid as a chelating agent and reducer. The microstructures and photoluminescence (PL) properties of the as-prepared YVO4:Eu3+ nanopowders were investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM) and PL spectroscopy. The luminescence intensities of the YVO4 nanoparticles doped with 5 mol% Eu3+ ions strongly depended on the calcination temperature, the molar ratio of citric acid to nitrates and the amounts of the Li+ additive. 相似文献
16.
Sol–gel derived Bi2Ti2O7 ceramic powders have been prepared from methoxyethoxides of bismuth and titanium (molar ratio of Ti/Bi = 1.23 and water/alkoxides = 1.31). The Bi2Ti2O7 phase was stable at a low temperature (700 °C), but it then transformed into mixed phases of Bi4Ti3O12 and Bi2Ti4O11 at 850–1150 °C. The single phase of Bi2Ti2O7 reoccurred at 1200 °C. Dielectric properties and ferroelectric behavior of samples sintered at 1150 and 1200 °C were examined. Under frequency of 1 MHz, samples sintered at 1150 and 1200 °C had a dielectric constant of 101.3 and 104.2, and a loss tangent of 0.0193 and 0.0145, respectively. Only the sample sintered at 1150 °C showed ferroelectric behavior, where remanent polarization is 3.77 μC cm−2 and coercive field is 24 kV cm−1. Thus, the Bi2Ti2O7 did not exhibit ferroelectricity, but the mixed phase of Bi4Ti3O12 and Bi2Ti4O11 did. 相似文献
17.
Effect of PWVA/Sb2O3 complex inhibitor on the corrosion behavior of carbon steel in 55%LiBr solution
The inhibition performance of PWVA/Sb2O3 complex inhibitor on carbon steel was studied in 55%LiBr + 0.07 mol L−1 LiOH solution. Results indicated that the complex inhibitor decreased both anodic and cathodic polarization current density and widened the passive potential region of carbon steel in test solution and can be classified as mixed inhibitor. The complex inhibitor exhibited excellent inhibition performance on carbon steel when the concentrations of PWVA and Sb2O3 were 300 and 200 mg L−1, respectively. With the solution temperature increasing from 145 to 240 °C, the corrosion rates of carbon steel increased from 4.71 to 120.66 μm y−1. In solution containing the complex inhibitor, the relationship between relative coverage ratio of inhibitor on carbon steel surface and inhibition efficiency at 145 °C was obtained as the equation μ = 0.94η, it was a direct proportion. This result proved that the complex inhibitor inhibited the corrosion of carbon steel by geometric blocking effect. When solution temperature was 160 °C, the adsorption Gibbs free energy of PWVA and Sb2O3 on carbon steel were −49.59 and −44.29 kJ mol−1, respectively. It indicated that the adsorption processes of PWVA and Sb2O3 on carbon steel surface were spontaneous processes. As a strong oxidant, PWVA facilitated the compact passive film comprising of FeO, Fe2O3 and Fe3O4 forming on the surface and itself was reduced to heteropoly blue. Sb2O3 adsorbed on carbon steel surface formed an adsorption film. PWVA and Sb2O3 behaved synergistic effect. The corrosion resistance performance of carbon steel in 55%LiBr + 0.07 mol L−1 LiOH solution was improved by PWVA/Sb2O3 complex inhibitor. 相似文献
18.
以Y2O3、Eu2O3、Bi(NO3)3·H2O、浓HNO3、偏钒酸铵、氨水、无水乙醇和一缩二乙二醇为原料,采用聚乙烯吡咯烷酮(PVP)辅助水热法合成YVO4: Eu3+, Bi3+纳米颗粒。使用X射线衍射(XRD)、扫描电镜(SEM)、红外光谱(IR)和荧光光谱(FL)等手段对产品进行了表征和分析。结果表明:合成的样品为YVO4: Eu3+, Bi3+纳米颗粒,均具有四方晶相结构,其微结构随反应溶液的的pH值变化。YVO4: Eu3+, Bi3+纳米颗粒在619 nm处有较强的红光发射(电偶极跃迁5D0→7F2),在594 nm有较弱的橙光发射(磁偶极跃迁5D0→7F1)。随着Eu/Bi比值的增大材料的荧光先增强后减弱,在Eu/Bi比值为5时样品的红光发射最强。溶液的pH值影响YVO4: Eu3+, Bi3+纳米晶的发光强度,其中pH值为10时的样品其红光发射最强。并探讨了YVO4: Eu3+, Bi3+纳米晶的发光机理。 相似文献
19.
Lithium has been inserted into, and extracted from, the spinel Li1.0V2O4 both electrochemically and chemically. Electrochemical and structural data show that in the system Li1+xV2O4, for 0 < x ≤ 0.5, Li+ ions are inserted into the interstitial octahedral sites of the Atet[B2]octX4 spinel structure. At x ≈ 0.5, Li+ ions in the tetrahedral A-sites are displaced into the remaining octahedral sites to yield, at x = 1, a rocksalt phase Li2V2O4; the [B2]X4 framework is unperturbed by the lithiation process. This framework also remains intact when Li+ ions are removed from Li1.0V2O4 to a composition Li0.67V2O4. Further extraction of lithium from the structure is accompanied by migration of some vanadium ions from the B-sites to the interstitial octahedral sites of the spinel structure. This process reduces the crystal symmetry from cubic to trigonal symmetry. In Li0.27V2O4 the structure resembles that of Li0.22VO2, obtained by delithiation of layered LiVO2, in which the vanadium cations are distributed in a 2:1 ratio between alternate cubic-close-packed oxygen layers; in the LiV2O4 spinel this ratio is 3:1. 相似文献
20.
Gadolinium-doped, yttrium oxide thin films have been deposited on silicon (001) substrates by radio-frequency (RF) magnetron reactive sputtering that exhibit cathodoluminescence (CL) at ultraviolet frequencies. The maximum CL brightness occurred at λ314–315 nm characteristic of the 6P3 / 2 → 8S (λ = 314 nm) transition observed in Gd-doped, yttrium oxide powders. The radiative recombination takes place at the rare earth activator Gd3+ site embedded in the Y2O3−δ host; the optical transition resides within the band gap of the Y2O3−δ host and the transition observed is characteristic of atomic gadolinium. A combinatorial approach to sputtering was used to deposit a film of variable composition from 1 to 23 at.% Gd in Y2O3−δ in order to rapidly discern the composition node of optimal CL brightness. A simulation was created for the purpose of predicting the film combinatorial composition for binary and ternary alloys prior to sputtering experiments in order to facilitate our combinatorial thin film synthesis technique. The model prediction varied from the real experimental composition profile by only 2.2 at.% Gd ± 1.6 at.% proving the predictor as a useful aide to complement combinatorial thin film experiments. A film of composition Y1.56Gd0.44O3.25 (8.3 at.% Gd) yielded the maximum CL brightness. CL brightness increased continuously up to the 8.3 at.% Gd composition due to the increased number of activators present in the host. Beyond this composition the brightness drastically decreased. The oxygen composition in the combinatorial film was strongly dependent on the Gd composition; films were sub-stoichiometric δ > 0 below 6 at.% Gd and was over-stoichiometric δ < 0 beyond this composition. 相似文献