Si4+-doped BaZr(BO3)2:Eu3+ phosphors are prepared by a conventional solid-state reaction.The influence of Si4+ addition on the charge transfer state of Eu3+-O2- and photoluminescence(PL) properties of BaZr(BO3)2:Eu3+ are discussed.Room temperature PL spectra indicated that efficient emission is obtained by Si doping.Increased values for the peak-peak ratio(PPR) of BaZr(BO3)2:Eu3+ at higher Si doping concentrations implied that the Eu3+ ion is located in a more asymmetric environment in BaZr0.8Si0.2(BO3)2:Eu3+ than in the undoped samples.The Judd-Ofelt parameters Ωλ(λ=2,4) were calculated from the PL data,giving results that were consistent with those from the PPR.The maximum radiative quantum efficiency was achieved at a Si doping concentration of 20 mol%.
ZHANG ZhongPengLI GuangMinZHANG XiaoSongXU ShengYanJI TingLI Lan
PbS quantum dots were prepared in the aqueous medium from readily available precursors. The shape of the particles isapproximately spherical, and the average particle size observed from HRTEM image was 7-8 nm. We applied PbS quantumdots and PMMA polymer to fabricate PbS quantum dots-PMMA composites, and investigate the photoluminescence PbSquantum dots in PMMA matrix with different mass ratio. PbS quantum dots in PMMA matrix have broad emission be-tween 900 nm and 1 500 nm and photoluminescence peak at 1 179 nm. Additionally, the photoluminescence intensityincreases with increasing the dopant concentration. PbS quantum dots-PMMA polymer composites can be potentially usedfor polymer optical fiber and electroluminescence (EL) in optical communication.
ZHANG Xiao-songDONG Xiao-yiLIU Yan-geKAI Gui-yunWANG ZhiLI LanHAN XuLI Yan
A large amount of one-dimensional ZnO nanorods with diameters in 15―50 nm aligned in radial cluster were successfully synthesized by polar polymer polyvinyl alcohol (PVA) as soft-template. The growth of ZnO nanorods was controlled by changing annealing temperature. The evolution of the morphology and microstructure was investigated by scanning electron microscope, transmission electron micro- scope and X-ray diffraction. It is shown that ZnO nanorods tend to be uniform and the crystallization is gradually improved with the temperature increasing from 400℃ to 700℃. The photoluminescence spectra of products show a strong ultra violet emission and relatively weak defect emissions. The sharp strong emission peak at 354 nm owing to the inter-band transition indicates the extraordinary photoluminescence property of ZnO nanorods.
LI JiangYongLI LanXU JianPingZHANG XiaoSongLI HaiYanZHUANG JinYan
The well crystalline YAG:Ce3+ phosphor was synthesized by solid-state method, and the temperature dependence of excitation and emission spectra of YAG:Ce3+ phosphor were investigated in the temperature range from room temperature to 573 K. With temperature increasing, it was noted that the emission intensity of as-prepared phosphors decreased considerably more rapidly when pumped by 460 nm than by 340 nm. The temperature-intensity curves under different excitation wavelengths were obtained using an Arrhenius function, and the corresponding activation energies were also obtained respectively. Thus, the experimental phenomenon was discussed in terms of nonradiative decay rate. The effects of as-prepared phosphors on the performance of the white LED with changing temperature were also studied.
A series of Y3Al5O12:Ce(YAG:Ce) phosphors doped with different Si 4+ concentrations is prepared by solid-state reaction.The temperature dependent characteristics of luminescent spectrum and decay time of Ce 3+ are investigated.With Si 4+ doped,the emission spectrum shows a blue shift due to a decrease of the splitting of 5d levels of Ce 3+ ion.The thermal stability is greatly improved by adding Si 4+ because the activation energy E increases from 0.1836 eV to 0.2401 eV.The study of the decay times against temperature for various doping concentrations of Si 4+ shows that the calculated nonradiative decay rate is affected by Si 4+ substitution.The results are explained by the configurational coordinate diagram.
