最新刊期
卷 10 ， 期 2 ， 1989
- 摘要：In this paper, the crystal field parameters of 5d state of Ce3+ ion in LaF3, LuF3, CaF2, SrF2 and BaF2 crystals were calculated. The calculated results are in good agreement with the experimental values. The mechanism, which causes the center of gravity of the 5d states to be lowered in crystals, was also discussed.162|67|2更新时间：2020-08-11
- 摘要：The quantum size effects and the pressure effects of CdSxSe1-x micro-crystals embedded in the glass matrix were studied.From the absorption and the emission spectra the quantum size effects were observed. The energy gap increases as the average size of the micro-crystals decreases.The pressure effects were investigated by measuring the blue shifts of the phonon peak and the exciton peak. The result shows that there exists a pressure as high as 20kbar in the sample,which should not be neglected when this kind of material is studied and applied.115|39|0更新时间：2020-08-11
- 摘要：The luminophors of Bi3+-doped and Bi3+, Eu3+-co-doped Ca2SiO4 were sythesised. The crystalline phase was checked by X-ray powder diffraction. By contrast, the d values of crystallogram are in agreement with that of ASTM file No.9-351. Therefore the products were determined to be mono-clinic 3-Ba2SiO4. The excitation and emission spectra were measured by RF-510 fluorospectrometer.The luminescent properties of Ca2SiO4:Bi3+ and Ca2SiO4:Eu3+, Bi3+ were investigated.We have found that Ca2SiO4:Bi3+ shows bright indigo-blue luminescence with max about 410nm under UV excitation. There are two bands in its excitation spectra, λmax=314nm and λmax=352nm respectively. When Bi3+ concentration increases, the excitation band of 314nm decreases rapidly and that of 352nm increases fast, and the ratio of the two band areas shows a linear relationship. The optimum concentration of Bi3+ ion for Ca2SiO4 is 0.02mol corresponding to 352nm excitation.The excitation spectra of Eu3+ emission for Ca2SiO4:Eu3+, Bi3+ appear a powerful broad band of Bi3+ with maximum value of 355nm besides excitation lines of Eu3+. Under excitations of 340nm, 355nm and 365nm UV radiation, the emission of Eu3+ (6D0-7F1, 5D0-7F2 transition) for Ca2SiO4:Eu3+, Bi3+ is increased more greatly than that of Ca2SiO4:Eu3+. Moreover, there is an intensive emission of Bi3+ with the maximum value of 390nm.Using 340nm UV radiation as excitation, Ca2SiO4:Eu3+, Bi3+ shows intensive emissions of Eu3+ corresponding ton 5D0-7F1 and 5D0-7F2 transitions, but Ca2SiO4:Eu3+ shows little emission under the same conditions. Results of these experiments show that there are energy transfer from Bi3+ ions to Eu3+ ions.Because the band overlapping of the emission band of Bi3+ with excitation lines of Eu3+ is in good condition, evidently, energy transfer from Bi3+ ions to Eu3+ ions is the cause of luminescence of Eu3+ sensitized by Bi3+99|49|9更新时间：2020-08-11
- 摘要：Luminescence of ZnTe crystal in the near band edge region has been investigated at 77K.Several explanations on the origin of near band edge emission have been reported. Cingolana et al[3]. considered the origin as band-gap shrinkage appeared under high excitation density, Jin et al[9]. considered it as bound-free transition,and Panowicz et al[5]. considered it as exciton-carrier scattering.In present work, crystals of undoped p-ZnTe were grown by Bridgman method and photoluminescence spectra were measured by Model 44W spectrometer with RCA-C31034 photomultiplier under excitation of 3371Å line of a N2 laser at 77-300K.The photoluminescence spectra of the ZnTe crystal under different excitation density at 77K are shown in Fig. 1.The spectra under lower excitation density consist of three bands peaked at 5252Å(E),5336Å(FB0)and 5394Å (FB1)respectively. With increasing excitation density the width of E band becomes large and its peak position shifts towards longer wavelength, but the peak positions of FB0 and FB1 bands do not change. The FB0 and FB1 bands correspond to free-to-bound transition and its replica associated with 1 LO phonon, respectively. The E band is caused by exciton-carrier interactions.106|45|0更新时间：2020-08-11
- 摘要：We have measured the fluorescence lifetime of emission peaks corresponding to 2E→4A2 and 4T2→4A2 transition for Cr3+:Y3Ga5O12 laser crystal under the temperature range of 10K to 300K. The radiative lifetimes of 2E, 4T2 and 4T2 are 965.8ns, 130.7ns and 88.6us respectively with the standard relative fitting deviation of 2.85%. The thermal quenching mechanism of fluorescence is investigated and some suitable relativities for the temperature dependence of fluorescence lifetime and radiative quantum yield are derived.107|56|2更新时间：2020-08-11
- 摘要：The band offset occuring at an abrupt hetero-interface in heterojunction materials and the carrier confinement behaviour at this interface have been studied for many years. A new photoluminescence (PL) spectrum, H-line, has been observed from the undoped or lightly doped GaAs/AlGaAs hetero-junction grown by LPE.The luminescence of H-line was shown between exciton and acceptor related transitions at low temperature, with peak energy ranging from that of the bound exciton to that of the shallowest acceptor transitions, increasing with the excitation intensity. Also, it dependents on the experiment temperature and the composition of heterojunction materials. The H-line can be considered to originate from the GaAs/AlGaAs interface. A few researches about the H-line and related behaviour have been done on MBE growth GaAs/AlGaAs heterojunctions. The purpose of this paper is to describe the X-ray diffraction and pico-second(ps)PL results about the H-line transition. A model of two dimensional exciton effect has been used successfully to explain the H-line experimental results.LPE GaAs/AlGaAs samples with similar heterojunction structure Were used to study the relation between H-line and the crystal quality. Double crystal X-ray rocking curves of (400), (511) and (322) diffractive directions and reflective topography of hetero-structure crystal were taken by a Rigakn CN 1518B1 scanning X-ray double crystal aiffractor. In the sample whose H-line can be observed, the half width of rocking curve is sharp, and the topography shows uniform stress distribntion and less deffects.The H-line would be missing in that samples with more deffects and ununiform stress distribution. It can be confirmed that the H-line comes from good heterojunction qnality with perfect interface.107|112|0更新时间：2020-08-11
- 摘要：In present paper, we study the difference of electroluminescence (EL) spectra of ZnS:Ho3+ and ZnS:HoF3 ACEL thin films. ZnS:Ho3+ and ZnS: HoF3 thin films are deposited by two separete boats in vacuum.The mechanism of EL excitation in ZnS:Ho3+ is discussed. The ratio of shorter wavelength emission intensity (490mn) to longer one (550nm) increases with applied voltage, shown as in Fig.3, we suggest that the EL in ZnS thin film doped with Ho3+ is generated by impact excitation of hot electrons. According to the EL decay behaviors of blue emission around 490nm (labled Ib) and red emission around 660 nm (labled Id), as shown in Fig. 4 and Table 1. it is indicated that the emissions of Ib and Id are the transitions from the same excited state 5F3 when the concentration of Ho3+ ions is lower.105|39|0更新时间：2020-08-11
- 摘要：In order to obtain white-emitting ACEL, some researchers[1,2] mixed two or three kinds of ACEL material. But the results were not so good. Others[4,5] reported some progress of white-emitting ACEL powder using homogenenous material. In present paper, we report some new results of preparing homogenenous white-emitting ACEL powder.The conditions for preparing samples are: 1) dopant concentrations, Cu2+ 0.2% and Mn2+ 0.05%-0.2% (weight), 2)temperature of firing 850-900C; 3) time of firing, 30-40min.The spectra of ZnS: Cu, Mn with different ratio of Cu/Mn under the excitation of 400Hz and 200V are shown in Fig.1. There appear three spectrum peaks at 4560Å, 5260Å and 5850Å in the limited concentration range of dopants. The peaks 4650Å and 5260Å aries from the luminescent center Cu and 5850Å arises from the center Mn. We have obtained the white-emitting ACEL phosphor with coordinates x=0.343, y=0.386 and the ratio of Mn/Cu=0.25. under the excitation of f=400Hz and 200V. The relation between brightness and excitation field is shown in Fig.2. It appears that the excitation process is collision-ionization or collision-excitation. We have also observed the relation between excitation field waveform and brightness waveform. The results are shown in Fig.3. It is clear that ACEL brightness Waveform of ZnS:Cu, Mr, is consisted of the overlap of Cu and Mn luminescence.112|54|0更新时间：2020-08-11
- 摘要：Copper-coating is one of the most important technique in DCEL, it can affects some significant properties of DCEL, such as forming process, lifetime and so on. Studies about this process are limited to technology conditions, its chemical reaction process has not yet been mentioned. This paper deals with some rules in copper-coating chemical reaction process for CaS:Ce and ZnS:Mn,Cu phosphors.Under normal conditions, the amount of coated copper on CaS:Ce or ZnS:Mn,Cu is seldom affected by concentration of copper,and it is gradually saturated with reaction time. This saturating amount relates to chemical properties and specific surface area of phosphor.Copper-coated amount increases with temperature in the function W=Ae-B/T. The relationship between velocity constant of copper-coating reaction and temperature is in accordance with the Arrhenius’s empirical formula.The copper-coating reaction can be distinguished in three different stages, these are the extremely rapid reaction in the initial stage, then the rapid reaction in the second stage, and the slow reaction in the final stage. It is suggested that the three different stages related to different suface defects of CaS or ZnS. Crystal edge on suface of polycrystal particles is a area of the highest chemical activity,so it can be considered that the reaction will firstly take place in this area. In the second stage the reaction may take place in crystal plane.The reaction in the final stage may take place in crystal boundary near the surface of particles. The chemical activity on these three kinds of area decreases in their given order, and which is in accordance with the reaction velocity of the three stages.Analysis of copper-coated amount on CaS:Ce in three different stages shows that the CaS particle will be coated one molecular layer of CuxS in the initial stage then 1-2,5 molecular layers in the second stage, and 2.5-3.5 molecular layers in the final stage, if We assumed that CuxS grows homogeneously on the particle surface. But in fact CuxS can not be grow in this way, its distribution relates to three different stages, so the variation of conductivity of phosphors also relates to three different stages or different surface defects. In the initial stage the conductive CuxS grows tnainly on the crystal edge, therefore a reticulated conductive phase will be formed and the conductivity is very low, for this net is not complete enough. In the second stage, this net will be expanded and cover all of the surface, and therefore the conductivity sharply increases with copper-coated amount. In the final stage conductive phase will be formed mainly on the crystal boundary near the partical surface, and it only gives small contribution to the conductivity, therefore it tends not to increase again.94|42|1更新时间：2020-08-11
- 摘要：In this report we have clarified that (1) pH of PVA-phosphor slurry and UV light intensity are correlated with the penetration depth of the incident UV light into dried PVA-phosphor screen; (2) particle surface, particle shape, particle size distribution etc.are correlated with scattering of incident UV light in a dried PVA-phosphor screen;(3) mean particle sizes determine a screen weight to give an optimal screen thickness;(4) a profile of the UV light intensity, exposure dose and development conditions are predominantly correlated with sharpness of phosphor dots or stripes.In aqueous solution amonium dichromate(AD), (NH4)2Cr2O7 hydrolyzes and several species of chromete ions:Cr2O7-2, HCrO4-2 and CrO4-2 exist in different ratious at different pH value and AD concentrations. But only HCrO4-2 ions respond on photosensitization of PVA. Fig. 1 shows the absorption spectra of aqueous solution at two pH values but the same AD concentration 2×10-4 mole per liter.The dependence of the HCrO4-1 concentration on pH value is shown in Fig. 2. The pH value must not be smaller than 7. otherwise the incident UV fight Will be totally absorbed by a thin surface layer of PVA film and no light will reach the substrate. Consequently the phosphor particles do not adhere on the substrate.Empirically it is shown that a simple maximizaton of the concentration of HCrO4-1 is not reality in screening of phosphor powder even if photoreaction of PVA(AD) resin is essential.Hence we must cosider the optical properties of PVA-phosphor screen with fhe assumption of small absorption coefficient of PVA(.AD) resin.Since the average size of phosphor particles is around 3 to 4um and the absorption coefficient of phosphor to the UV light is estimated to be 105 per cm (0.1μm depth), the UV light never penetrates through the particles. The photoreaction of PVA (AD) resin at substrate occurs mainly due to the absorption of scattered UV light by phosphor particles.The scattering in phosphor srecen increases as optical irregularity of phosphor is increased. And after baking process the dried adhesion of particles decrease as particle size is increased.Te minimum size required meets also the requirement of high optimum brightness, approximately 3 to 4um. Maximum scattering is expected with round particles.Further the distribution of particle size should be according to log-normal probability.This says that the particles are primary (i.e.no aggregated particles). Fig.6 illustrates a tool for study of screening conditions.The screen is dried after screening of PVA-phosphor slurry and is exposed by the UV light through an attenuator filter which changes its transmittance continuously from 100% to 20%.Adhesion of phosphor particles is determined from the threshold angles at which the screen defects start after development.Then we discussed the problems of optimum screening Weight per cm2, profile of UV light intensities on phosphor screen and cross contamination.121|109|0更新时间：2020-08-11
- 摘要：Energy transfer in rare earth (RE)-organic complexes materials and their luminescence properties have obtained extensive attention in the recent years. Studies of luminescence regarding to polymer compelxes of RE are particularly interesting. We have demonstrated that the energy transfer from the bpy (2,2’-bipyri-dine) to the central Ce3+ ion for the Ce3+-bpy complex solution and reported that the complexation of Ce3+ with the polemers and the fluores cence properties of the compexes in the preceding papers.In this paper, we described relation between the excitation process of Ce3+ fluorescence and the structures for the two complexes. The polymer complexes of Ce3+ are Ce3+-polymethylmethacrylate, Ce3+-PMMA and Ce3+-poly-(2-methacryloyloxymethy-1,4,7,10,13,16-hexaoxacyclotodecane), Ce3+-PMAl8·C·6,respectively.102|61|1更新时间：2020-08-11
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