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YPO_4 nanocrystals: preparation and size-induced lattice symmetry enhancement

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Journal of Rare Earths 2008年第4期26卷 495-500页

作者：刘琼苏毅国于洪生韩炜 College of Physics Jilin University Fujian Institute of Research on the Structure of Matter Chinese Academy of Sciences

YPO4 and Eu doped YPO4 nanocrystals were prepared via a simple hydrothermal method. The phase purity, rnicrostructure, surface absorbed water and luminescence properties were characterized with X-ray diffraction （XRD）, transmission electron microscopy （TEM）, fluorescence spectrum, infrared spectroscopy, Raman spectroscopy and thermogravimetry analysis（TGA）. Combined with XRD and TEM analysis, it was found that YPO4 nanocrystals crystallized into a single phase of tetragonal （141/amd） zircon structure. YPO4 nanocrystals showed a size reduction with the reaction temperature decreasing. Considering the XRD, IR and Raman results, a lattice expansion and the unit cell symmetry enhancement were observed with the particle size decreasing. A dipole to dipole interaction model was applied to investigate the relationship of the variation of microstrucmre and the particle size. The emission spectrum of Eu doped YPO4 nanocrystals was also presented and the emission bands were clearly ascribed to the f to f transitions of Eu^3＋.

关键词： hydrothermal lattice expansion symmetric enhancement blue shift luminescence rare earths

Effect of high temperature annealing on strain and band gap of GaN nanoparticles

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Chinese Physics B 2010年第8期19卷 495-499页

作者：肖洪地毛宏志林兆军马洪磊 School of Physics Shandong University School of Chemistry and Chemical Engineering Shandong University

Black-coloured GaN nanoparticles with an average grain size of 50 nm have been obtained by annealing GaN nanoparticles under flowing nitrogen at 1200 ℃ for 30 min. XRD measurement result indicates an increase in the lattice parameter of the GaN nanoparticles annealed at 1200 ℃, and HRTEM image shows that the increase cannot be ascribed to other ions in the interstitial positions. If the as-synthesised GaN nanoparticles at 950 ℃ are regarded as standard, the thermal expansion changes nonlinearly with temperature and is anisotropic; the expansion below 1000 ℃ is smaller than that above 1000 ℃. This study provides an experimental demonstration for selecting the proper annealing temperature of GaN. In addition, a large blueshift in optical bandgap of the annealed GaN nanoparticles at 1200 ℃ is observed, which can be ascribed to the dominant transitions from the C（FT） with the peak energy at 3.532 eV.

关键词： GaN nanoparticles thermal expansion strain blue shift bandgap

Adjustable Luminescence of SrAl_2O_4:Eu^(2+),Dy ^(3+) Assembled in Zeolite

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Journal of Rare Earths 2004年第1期22卷 100-103页

作者：刘应亮王晓华张静娴容建华黄浪欢袁定胜 Department of Chemistry

Capsulating guest into the nanometer voids of zeolites is a effective way to form novel host-guest material. In our work, stoichiometric SrAl2O4 : Eu2+, Dy3+ sol guest was prepared by sol-gel method and assembled into the nanometer channels of zeolite ZSM-5 host through mechanical mixing, hydrothemial reaction and microwave heating reaction, respectively. After being reduced and diffused in a microwave muffle, the fluorescence spectra of the host-guest materials exhibit remarkable blue shifts in companison of that of SrAl2O4 : Eu2+, Dy3+ Some interesting phenomena in the assembled host-guest materials are that the after-low emission spectra exist two bands at about 400 nm and 517 nm and the relative strengths of these two hands can be adjusted by changing the assembly methods and the assembly concentration. These are attributed to the fact that the phosphor was capsuiated into the voids of zeolite ZSM-5 and generated the quantum size effect and the host-guest effect.

关键词： zeolite assemble blue shift adjustable phosphorescence rare earths

Synthesis and luminescence properties of Mn4+-dopant Ca14Zn6Ga10-xAlxO35solid solution

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Progress in Natural Science:Materials International 2018年第3期28卷 301-307页

作者： Yiyang Zhou Weiren Zhao Chongrui Lu Zifeng Liao School of Physics and Optoelectronic Engineering Guangdong University of Technology

Mn4+-activated oxide phosphors,owing to their desirable spectral features,eco-friendly and low cost,are emerging as a new class of non-rare-earth red phosphors for warm white ***,these phosphors possess low photoluminescence quantum efficiency excited by blue chip *** we report an isostructural solid solution of Ca14Zn6Ga10-xAlxO35:0.15Mn4+（0≤x≤10）synthesized by a traditional solidstate reaction *** microstructure and luminescent performance of this red-emitting phosphor are investigated in detail with the aids of X-ray diffraction,diffuse reflection spectra,photoluminescence spectra/decay/QE,and temperature-dependent PL/QE *** shift of energy peaks of4A2→4T1and4A2→4T2transition is illustrated by the Tanabe–Sugano diagram and the configurational coordinate *** crystal field strength（Dq）and the Racah parameters（B and C）are carefully calculated to estimate the nephelauxetic effectβ*** we achieve external and internal quantum efficiencies as high as26.1%and 40.3%for Ca14Zn6Ga6Al4O35:0.15Mn4+excited by 466 nm,the highest one ever reported in Mn4+activated oxide phosphors under the similar condition.

关键词： Crystal phase Quantum efficiency Red emission blue shift

Substituent Effects on the blue-shifting Hydrogen Bonds between X-C≡C-CF_2-H and Water

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Chinese Journal of Chemistry 2002年第3期20卷 247-251页

作者：范剑淼张科春刘磊李晓松郭庆祥 Department of Chemistry University of Science and Technology of China Hefei Ahui 230026 China

MP2/6-31 + g(d) calculations were performed verifying the existences ofblue-shifting X - C ≡ C - CF_2 - H···OH_2 hydrogen bonds. Detailed analyses revealed that theinteraction energy and donor-acceptor distance had good correlations with the substituent Hammettconstants. However, the extent of C―H bond contraction and the blue shift of the C―H stretchingvibration did not show any good correlation with the traditional substituent constants, indicatingthat certain more complicated mechanisms might be involved in the present systems. Nevertheless, itwas found that highly electron-withdrawing susbtituents were not favorable to the C―H bondcontraction, and it was suggested that the attractive interaction between water and the carbon of -CF_2H probably played an important role in the blue shift.

关键词： hydrogen bond blue shift vibration bond contraction substituent effect

Influence of Ga^(3+) on Photoluminescence of Ce^(3+)

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Journal of Rare Earths 1998年第2期16卷 16-20页

作者：徐春祥娄志东刘行仁徐叙瑢

The electro optical characteristics of SrS∶Ce and SrGa 2S 4∶Ce as two kinds of hopeful blue TFEL phosphors have been intensively investigated. The color purity of SrGa 2S 4∶Ce is better than that of SrS∶Ce. In this paper, the influence of Ga 3+ on photoluminescence (PL) characteristics of Ce 3+ is first reported. Ga 2S 3 was doped into SrS, then sintered. The emission spectra shift obviously towards short wavelength range with increase of Ga 3+ concentration. At the same time, the relative intensity of the excitation peaks corresponding to the interband absorption of SrS reduces, and the excitation efficiency corresponding to the transition from the ground state to the excited state of Ce 3+ ion increases. The ligand field around Ce 3+ is changed by doped Ga 3+ . The ionicity of the substituted become stronger and Ce 3+ -Ce 3+ interaction become weaker. These are favorite to blue emission.

关键词： Rare earths SrGa 2S 4∶Ce blue shift Excitation efficiency Ligand field Ce 3+ -Ce 3+ interaction

Photoluminescence Spectra of Post-heat-treated Porous Silicon

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Semiconductor Photonics and Technology 2002年第4期8卷 234-237页

作者： LIU Xiao bing, SHI Xiang hua (Dept. of Phys. and Inform. Tech ., Changsha Univ. of Electr. Power, Changsha 410077, CHN) Dept. of Phys. and Inform. Tech. Changsha Univ. of Electr. Power Changsha 410077

Porous silicon prepared by pulse electro-etching is heat-treatedin O_2 atmosphere with an enhancement of its PI. peak and animprovement of its PL stability. The PL peak of a sample poroussilicon treated in O_2 atmosphere at 1000 ℃ presents itself a three--peak structure and, compared with an un-- heat--treated sample,there exists blue shift of ～ 40 nm.

关键词： Heat treatment blue shift Stability

The Influence of Rapid Thermal Annealing on SiGe/Si Multiple-Quantum Wells p_-i_-n Photodiodes

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Journal of Semiconductors 2001年第6期22卷 695-699页

作者：李成杨沁清王红杰王玉田余金中王启明中国科学院半导体研究所集成光电子国家重点实验室北京100083

The influence of thermal treatment on Si 1-x Ge x/Si multiple-quantum wells (MQW) p-i-n photodiodes has been investigated by photocurrent spectroscopy combined with X-ray double crystal *** cutoff wavelength is significantly reduced due to the Si-Ge interdiffusion and partial relaxation of the strained SiGe *** values of the blue shift increase slowly with the annealing temperatures in the range of 750℃ to 850℃.However,the nonlinear changes in photocurrent intensities of the samples annealed at different temperatures have been observed,which is mainly dominated by the generation of misfit dislocations and the reduction of the point defects in the heating process.

关键词： SiGe/Si MQW photodiodes blue shift thermal annealing interdiffusion