最新刊期
卷 34 ， 期 4 ， 2013
- 摘要：Phosphors Ca9(1-x-y)Al(PO4)7:xCe3+,yDy3+ were synthesized by solid-state reaction method at high temperature under a reducing atmosphere of CO, and the luminescent properties of the phosphors were investigated. The X-ray diffraction patterns (XRD) show that a pure phase of Ca9Al(PO4)7 phosphor has been obtained after calcined at 1 200℃. Under 268 nm excitation, the Ca9Al(PO4)7:Ce3+ sample exhibits a broad emission band centered at 363 nm. The emission spectrum of Ca9Al(PO4)7:Dy3+ sample under 350 nm excitation shows two characteristic emissions of Dy3+ located at 483 nm and 574 nm, corresponding with 4F9/2→6H15/2 and 4F9/2→6H13/2 transition, respectively. According to the fluorescence spectra, the characteristic emissions of Dy3+ are significantly sensitized by Ce3+ when the Ca9Al(PO4)7 samples are co-doped with Ce3+ and Dy3+. Adjusting the concentration of Ce3+ and Dy3+, the color of the phosphors can change from yellowish-white to white. The results indicate that the optimal mole fractions of Ce3+ and Dy3+in Ca9(1-x-y)Al(PO4)7:x Ce3+,yDy3+ are x=0.02 and y=0.02, and the chromaticity coordinate is (0.306, 0.313).关键词：Ca9Al(PO4)7：Ce3+;Dy3+;white emitting phosphor;luminescence;color coordinate87|73|1更新时间：2020-08-12
- 摘要：The Er3+,Yb3+ co-doped Gd2WO6 phosphors were prepared with co-precipitation method. Electric dipole-dipole interaction between Er3+ in Er3+,Yb3+-doped Gd2WO6 phosphor is demonstrated from the curve of concentration quenching. By analyzing the temperature character of the phosphors, the activation energy of samples with 5% and 20% doping mole fractions is obtained and the experimental values are 0.27 and 0.29 eV, respectively. The temperature characters of samples with two different doping concentrations are analyzed by means of fluorescence intensity ratio from 2H11/2→4I15/2 and 4S3/2→4I15/2 radiative transitions, indicating good temperature sensor for the present materials.关键词：phosphor;Gd2WO6：Er3+;Yb3+;concentration quenching;temperature sensing107|178|3更新时间：2020-08-12
- 摘要：Three-dimensionally ordered macroporous (3DOM) ZrO2 inverse opal materials prepared by polystyrene (PS) colloidal crystal templating, using the sol-gel method, were successfully fabricated. The structure of 3DOM ZrO2 was determined by X-ray diffraction (XRD) and scanning electron microscope(SEM). The results show that the produced ZrO2 are arranged orderedly macropores with average diameter of 180 nm. The spectra show both intrinsic F centers emitter and impurity emitter exist in wide band gap ZrO2.The mechanism of the phosphorescence was formulated using a simplified scheme.关键词：three-dimensionally ordered macroporous(3DOM);ZrO2;colloidal crystal template;luminescence106|91|0更新时间：2020-08-12
- 摘要：A series of fluorescent powders of Gd2-xO2SO4:xEu3+ have been synthesized by two methods: the co-crystallization followed by calcinations (CCC) method and the co-mixture followed by calcinations (CMC) method. The as-prepared phosphors were examined by means of X-ray diffraction (XRD), scanning electron spectroscopy (SEM) and photoluminescence spectrometer (PLS). The results show that Gd2-xO2SO4:xEu3+ phosphors with single crystalline phase have been successfully prepared with both methods at calcinations temperature around 950℃, and emit red light at 618 nm under ultraviolet exitation. However, the emission strength and particle characterization are different. It is proved that the phosphors prepared by CCC method have stronger red emission and better morphogy of the particles than that by CMC method. The optimal Eu doping content and calcinations temperature are determined to be x=0.1 and 950℃. The particle size of as-synthesized phosphors is around 500 nm.关键词：gadolinium oxide sulfate;co-crystallization;phosphor;preparation173|142|3更新时间：2020-08-12
- 摘要：The red long-lasting phosphor Y2O2S:Eu3+,Mg2+,Ti4+ was synthesized by sol-gel method using EDTA as complexing agent. XRD, SEM and spectra fluorophotometer technique were used to investigate the performance of samples synthesized at different temperatures. When the sulfuretted temperature is below 1 000℃, the product is a mixture of Y2O3 and Y2O2S. The pure phase of Y2O2S is obtained when the temperature is 1 050~1 100℃.When the temperature rises to 1 150℃, the phase of Y2O3 appears again. When the temperature is 950~1 100℃, the size of particle is about 50~300 nm. From the spetrum, the main emission peak lies at 626 nm under the 330 nm excitation, which is ascribed to the transition of Eu3+ from 5D0 to 7F2. The optimal afterglow time of the sample is 95 min (≥1 mcd/m2) when the sulfurization temperature was 1 100℃. Compared with sol-gel method using acetyl acetone as complexing agent, the afterglow properties of samples synthesized by sol-gel method using EDTA as complexing agent have been greatly improved.关键词：red long-lasting;Y2O2S：Eu3+;Mg2+;Ti4+;sol-gel method;EDTA154|130|1更新时间：2020-08-12
- 摘要：ZnS:Mn quantum dots were prepared by hydrothermal method. The effect of the doping concentration of ZnS:Mn quantum dots on crystal structure and luminescent properties was discussed. The quantum dots were characterized by the fluorescence spectroscopy. The results indicated that ZnS:Mn quantum dots exhibited the strongest emission at 595 nm, with 2% doping mole fraction, then with doping concentration increasing, the intensity of luminescent decreased due to the fluorescence quenching phenomenon. The effect of surface modification on the morphologies and luminescent properties of quantum dots were also discussed. Transmission electron microscope (TEM) images indicated that the surface aggregation phenomenon of ZnS:Mn quantum dots was improved with the MPA surface modification, the quantum dots also exhibited single size and good dispersibility properties, the average particle diameter was about 5 nm. In addition, the surface non-radiation defect centers were reduced, which caused emission peak intensity increasing at 595 nm by Mn2+ doping. The surface modified ZnS:Mn quantum dots were conjugated with bovine serum albumin (BSA) molecules. In BCA detection, the results indicated that the surface modified ZnS:Mn quantum dots had the better biological conjugation property.关键词：ZnS:Mn;surface modification;luminescence;BCA detection115|130|2更新时间：2020-08-12
- 摘要：YAG:Ce3+ phosphors with regular spherical morphology and different particle size distribution were successfully prepared by solid-state reaction followed by sieving method. XRD analysis revealed that crystal lattice parameters nearly unchanged with the variation of particle size. The effect of particle size distribution on optical properties was investigated by spectrophotometer. The results indicated that the absorption of blue light and emission intensity of phosphors simultaneously decreased with decreasing of particle size. Meanwhile, the maximum emission wavelength showed blue shift and chromaticity shifted toward green region with smaller particle size. The packaging performance suggested that the reduction in particle size will result in reduction of luminous efficiency. In contrast, the colour temperature (Tc) and general colour rendering index (Ra) increased with decreasing of particle size.关键词：phosphors;optical properties;particle size;white LEDs127|594|2更新时间：2020-08-12
- 摘要：ZnAl2O4:Tb3+ green phosphors were prepared by an improved co-precipitation method. The crystal structure, phase transition and luminescence properties of as-synthesized ZnAl2O4:Tb3+ phosphors were investigated by X-ray diffraction, TG-DTA and fluorescence spectrometer, respectively. XRD results indicate that the crystal structure of the phosphors is cubic phase of ZnAl2O4 and the best temperature for synthesis ZnAl2O4:Tb3+ with cubic structure is 700℃. The excitation spectrum is formed by a broad band (260~310 nm) and a series of sharp peaks. The emission spectrum is composed of several peaks,located at 490, 544, 590 and 624 nm, respectively. The main peak is at 544 nm which is contributed to Tb3+ ions transition from 5D4 to 7F5. It is found that Tb3+ concentration has a significant effect on the emission spectrum. When Tb3+ mole fraction is 5.8%, the green emitting is the strongest. However, When Tb3+ mole fraction is more than 5.8%, the luminescence intensity decreases.关键词：co-precipitation method;ZnAl2O4：Tb3+;luminescence properties99|78|2更新时间：2020-08-12
- 摘要：Sr3SiO5:Eu2+ phosphors were synthesized by high temperature solid state reaction method under a reductive atmosphere. The effects of Ba2+ substitution for Sr2+ and fluxes on the crystal structure and the luminescent properties of Sr3SiO5:Eu2+ phosphors were investigated by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), and fluorescence spectrophotometer. The substitution of the host lattice cation Sr2+ by Ba2+ can make the polyhedron enlarged and then cause the shrinking of the neighboring Sr2+ or Eu2+ sites, which may explain an increased crystal field. Along with the increase of the Ba2+ concentration, Eu2+ occupies the Ba2+ site by degrees and the crystal field decreases. Thus, the emission wavelengths of the sample display red-shift from 575 nm to 592 nm at first and then blue-shift back to 583 nm. The maximum emission wavelength appears when n(Sr):n(Ba)=4. The experimental results also indicate that the influence of different flux on the luminescent intensity of the Sr3SiO5:Eu2+ phosphors varied: H3BO3 decreased sharply, NH4F improved a little and NH4Cl improved greatly. The optimum mass fraction was 2% for NH4F and 0.3% for NH4Cl, respectively.关键词：Sr3SiO5：Eu2+;crystal structure;emission intensity;fluxes98|155|0更新时间：2020-08-12
- 摘要：The transparent glass-ceramics containing PbF2 microcrystals were prepared by high temperature melting-quenching and thermal treatment method. X-ray diffraction pattern proved that the crystallites in the glass-ceramic are β-PbF2 microcrystal particles. The average size of the microcrystals is about 15~75 μm. Both X-ray fluorescence and photoluminescence intensity in the glass ceramics increase significantly compared with the as-made glass. The influence of crystallization on the luminescence intensity of glass ceramics is discussed.关键词：PbF2 microcrystals;glass ceramic;photoluminescence;X-ray excited emission112|231|0更新时间：2020-08-12
- 摘要：Using non-toxic and non-corrosive sulfur hexafluoride (SF6) and D2 as working gas, the influence of the ratio and total pressure of the mixture gas on the performance of non-chain pulsed DF laser with a stable optical resonator is investigated. The research is based on UV-preionized transverse discharge method. The results show that the optimum ratio and total pressure of the SF6 -D2 mixture gas, are 10:1 and 10.5 kPa, respectively. By using the DF laser spectrum analyzer to measure the output spectrum of DF laser, 17 P-branch transition lines are attained, which the laser energy concentrates in several lines near the 3.876 μm line. The laser beam divergence angles in both horizontal and vertical directions are 1 mrad, which is obtained by using the laser ablation method. The maximum single pulse energy of 3.58 J, pulse duration of 215 ns, peak power of 16.65 MW, and electro-optical conversion efficiency of 2.08% are achieved under the best working conditions when the charging voltage is 39 kV.关键词：pulsed DF laser;UV-preionized;electric-discharge;non-chain;output characteristics95|147|5更新时间：2020-08-12
- 摘要：Metallic nano-hole array based color filter is showing the great potential application for OLED. In this paper, we propose the metallic nano-hole array based filter in large area by employing colloidal etching and vacuum depositing technology. To ease the fabrication, the structural parameters of the nano-hole array on the transmittance of the red light as well as the bandwidth is systematically studied and analyzed. The simulation results indicate that when the diameter of the nanohole is 240 nm and the film thickness is 120 nm, the transmitted resonant wavelength for red display is 704.06 nm, the intensity transmission is 52%, and the bandwidth is only 24.8 nm. The simulation results provide a theoretic guide for the fabrication of metallic nano-hole array by PS sphere's etching and vacuum depositing technology.关键词：OLED;color filter;colloidal crystal;intensity transmittance127|243|0更新时间：2020-08-12
- 摘要：The influence of the carrier mobility on the performances of organic solar cells was studied using the simulation method. It is found that the mobility influences the carrier generation and transport simultaneously. There is an optimal value both for electron mobility and hole mobility. The mobility larger than the optimal value will lead to a small increase in the short circuit current. The mobility smaller than the optimal value will result in the insufficient dissociation of the photogenerated electron hole pair, and decrease the short circuit current and the fill factor.关键词：organic solar cells;mobility;short circuit current;open circuit voltage;fill factor143|389|1更新时间：2020-08-12
- 摘要：A series of InGaN/GaN multi-quantum wells(MQWs) samples were grown with four different showerhead gap position using Aixtron 3×2 close-coupled showerhead MOCVD system. In the reactor, the showerhead gap position of 7, 13, 18 and 25 mm were selected to study the effect of gap position on the growth of InGaN/GaN MQWs. The surface morphology, interface quality of samples were characterized by atomic force microscopy(AFM) and X-ray diffraction(XRD). The results show that the roughness of MQWs decreased and the interfacial structure between InGaN and GaN deteriorated simultaneously with the increasing of the showerhead gap position. The thickness of GaN barrier layer and InGaN well layer also decreased, as well as the In composition. However, when the showerhead gap position was enhanced to a certain level, both the variation in thickness of the MQWs and the In composition were reduced and tended to stay stable. Meanwhile, compared with the thickness variation of barrier layer and well layer, the thickness variation of barrier layer was more remarkable.关键词：MOCVD;showerhead gap position;InGaN/GaN MQW116|143|0更新时间：2020-08-12
- 摘要：External-cavity lasers (ECLs) play an essential role in numerous areas such as optical telecommunication, environment monitoring, medical treatment, and spectroscopy. Due to unique features of the quantum dot material, i.e., low density of states and broad gain profile, quantum dot lasers are really suitable for high performance ECLs. The frequency stability and the linewidth can be improved by using an external cavity. However, optical feedback may cause instabilities. It is important to know the characteristics of a semiconductor laser with external optical feedback in such systems. The common Littrow-type external cavity laser contains a collimating lens and a diffraction grating as the end mirror. The first-order diffracted beam provides optical feedback to the laser diode chip, and the emission wavelength can be tuned by rotating the diffraction grating. In this paper, the theory of grating external cavity quantum dot lasers is discussed. The influences of external cavity feedback on output power and maximum tuning range of the Littrow-type external cavity quantum dot laser are analyzed. Device parameters have a significant impact on the external cavity laser performance. Output power and tuning range of external cavity quantum dot lasers are numerically simulated and compared with the experimental results. The theoretical results of output power agree well with the experimental data, and the tuning range value is slightly less than the experimental results without considering the suppression relative to nonlinear gain.关键词：quantum dot laser;external feedback;output power;tuning range95|250|2更新时间：2020-08-12
- 摘要：Current blocking layer (CBL) was used to improve light output power and luminous efficacy of the LEDs.The structure of CBL can block the current from entering the active region below the top contact. The shape of current blocking layer impacts properties of LEDs, so we fabricate different kinds of SiO2 CBL by plasma enhanced chemical vapor deposition (PECVD)and etched. There are 3 shapes in the experiment: Group A has a whole structure of CBL which approximately has a same shape of top metal contact laver, group B is a Y-shaped which located on top of the upper confinement, and group C only has a point-shaped structure under the metal pad electrode. According to the experiment, we obtain that the difference of voltage between different groups is not too large in low power LEDs, when CBL and P-electrode have the same shape, the LED has the best properties and by 14.6% compared to that of conventional LEDs.关键词：light-emitting diodes(LEDs);current blocking layer(CBL);luminous efficacy109|165|3更新时间：2020-08-12
- 摘要：The multi-layer microcavity OLEDs have been fabricated with hole transport layers of CBP and TCTA, an emissive layer of Eu(DBM)3Bath, and an electron transport layer of TPBI. Multicolor electroluminescence from the transition of Eu3+ iron with three peaks at 580 nm (5D0→7F0), 612 nm (5D0→7F2), and 652 nm (5D0→7F3) was achieved by changing the transition rate between the different energy levels of Eu(DBM)3Bath through optical microcavity. The microcavity OLED device with an EL peak of 612 nm shows the maximum current efficiency more than 20 cd/A, and maximum luminance over 1 300 cd/m2.关键词：organic;microcavity;europium-complex;electroluminescence93|99|0更新时间：2020-08-12
- 摘要：Taking antibiotic medicine as an example, the interaction between bovine serum albumin (BSA) and cefpiramide sodium (CPMS) was researched at different temperatures in the simulation of the human body physiological conditions. A theoretical model of predicting the binding rate of drug to human plasma protein was estimated according to the binding constants and the number binding site in this reaction. Based on the experimental data, the regular pattern of the binding rate of drug to plasma protein was analyzed when the concentration of CPMS and BSA was dynamically changed. The results showed that the binding rate of drug to human plasma protein was dynamically changed in different concentration of protein and drug conditions. Besides, the binding rate of drug to plasma protein was forecasted on the basis of binding constants and the number binding site in the reaction of drug and protein in literature, and it showed a satisfied result compared with the data in literature.关键词：drug and plasma protein;binding ratios;fluorescence quenching method;forecast90|302|1更新时间：2020-08-12
- 摘要：Several new photonic quasicrystal fibers(PQFs) with ultra-flattened chromatic dispersion at wide range of the telecommunication-window are presented. Based on the full vectorial model, the finite element method is adopted to analyze the dispersion properties of photonic quasicrystal fiber with double-clad structure. According to the numerical simulation results of the PQF1, the dispersion of the photonic quasicrystal fiber can be controlled within -2.41±0.28 ps/(km·nm) in 1.45~1.65 μm optical communication-window. Afterwards, we get a near-zero flattened dispersion curve by increasing the hole spacing. In a wide wavelength range from 1.350 to 1.736 μm, the region of dispersion variation is from -0.45 to 0.57 ps/(km·nm). For PQF2, the dispersion value can be controlled within 4.795±0.355 ps/(km·nm) by adjusting the parameters in the wavelength range of 1.45 to 1.68 μm.关键词：fiber optics;flattened dispersion;finite element method;photonic quasicrystal fibers(PQF)106|155|0更新时间：2020-08-12
- 摘要：The dispersion equation of depolarized-guided acoustic wave Brillouin scattering (De-GAWBS) in photonic crystal fiber was numerically solved. The relationship of Brillouin frequency shift with pump wavelength and air hole filling fraction was studied. The dependency of De-GAWBS frequency shift on temperature, tensile strain, acoustic modes, the core diameter of photonic crystal fiber, and the number of air hole layers was investigated. The Brillouin frequency shift decreases linearly with the wavelength increasing, and the transverse velocity of acoustic wave decreases with the increasing of the air hole filling fraction at the same wavelength. The De-GAWBS frequency shift increases linearly with the increasing of temperature and strain. The frequency shift of the higher order torsional-radial mode is more sensitive in the same temperature condition, and the frequency shift of the lower order torsional-radial mode is more sensitive in the same tensile strain condition. The resonance frequency shift increases with the core diameter increasing and decreases with the number of layers of air hole increasing.关键词：depolarized guided acoustic wave;Brillouin scattering;photonic crystal fiber;temperature;tensile strain98|139|3更新时间：2020-08-12
- 摘要：A lossless compression system for multi-spectral TDICCD images consisting of few bands is proposed. The compression scheme has two main steps. The first is that a 5/3 integer lifting wavelet transform, which is implemented by proposed SPE structure, is used to reduce spatial correlation. The second is that the wavelet detail coefficients are predicted according to the proposed statistical dependence between the wavelet coefficients to reduce both the inter-bands and remaining intra-band correlation. To output the compressed stream, the predicted residual error is encoded using an entropy coder. Finally, the verification experiments to the lossless compression system of multi-spectral TDICCD images using ground test equipment were carried out. The experiments results showed that the proposed compression system can work fast, reliably and stably. The lossless compression rate is reached 1.544 bits/pixel. Compared with traditional approaches, the proposed method could improve the average compression rate by 0.336 bits/pixel. The compression system can work properly at different sideways. The maximum time of compressing one frame image is only 26.446 ms. It effectively solves the difficult of hardware implementation of the whole wavelet-based compression scheme and improves the average lossless compression rate.关键词：multi-spectral space camera;lossless compression;SPE element;wavelet coefficient dependences;wavelet coefficient prediction110|154|1更新时间：2020-08-12
- 摘要：According to the heat dissipation characteristics of a project lamp with high power LED array, the physical model of key structures for heat dissipation was established. And some mathematic models, which can express correctly the heat conduction and natural convection performance of above physical model, were selected based on equivalent thermal circuit method. Using these models, the heat dissipation performance of LED array was calculated in EXCEL software following the specified calculation procedure in this paper. Through comparison between the calculated temperature and the measured data obtained by infrared thermal imager, the calculation error of mean temperature is as low as +1.08%, so the validity of thermal circuit method is satisfactory for the given LED model. Subsequently, the influence trends of three key structural parameters on heat dissipation were analyzed separately in detail. The results show that heat dissipation performance can be improved obviously with an optimum fin spacing about 5 mm, and a higher fin height or a thinner fin thickness all can obtain a lower junction temperature, however, the best values of fin height (24 mm) and fin thickness (1~2 mm) should be determined to satisfy the demands of weight reduction, low-cost and manufacturability. Therefore, thermal circuit method can be effectively applied to thermal analysis and parameters optimization with the advantage of accuracy and swiftness.关键词：LED array;thermal circuit method;natural convection;heat dissipation performance137|218|5更新时间：2020-08-12
- 摘要：The powerful ability of generating multi-way spectral data in modern spectrum instruments makes multi-way spectral quantitative analysis method become one of the important topics. Since the multi-way spectrometry is represented as a tensor, a new multi-way spectral quantitative analysis method based on support tensor machines (STM) is presented. The presented methods preserve the intrinsic structure of the multi-way spectrometry. Due to the reduction of model parameter number, the methods represented by tensor reduce the over-fit problem in the case of small samples. Unlike the conventional methods such as parallel factor analysis (PARAFAC) and multi-way partial least squares (N-PLS), the presented methods do not need to estimate the component number. The experiments for detecting chemical oxygen demand (COD) and total organic carbon (TOC) in water are carried out. The experimental results show that the presented methods are improved with comparison to the existing multi-way spectral quantitative analysis methods, and the models are not sensitive to the pre-determined parameters C and ε.关键词：multi-way spectrometry;quantitative analysis;support tensor machines;calibration model129|95|1更新时间：2020-08-12
- 摘要：In order to solve the problem that it is hard to quickly and accurately calculate the coordinate of the intersecting point between the mapping line and the gamut boundary, an iterative calculation method based on improved CORDIC algorithm is proposed, which can approach to the intersection point. Using the characteristics of CIE LUV color space, this method can approach the point along the mapping line. It can save a lot of storage resources and computing time because it has no processes of boundary search and interpolation calculation. In addition, it has high calculation accuracy and wide applicability. This paper analyzes the calculation algorithm's principle, precision and speed. Boundary calculation and the error analysis have been made on D65 light LED display source. The experimental results show that the fitting boundary is very smooth after 12 iterations the and the maximum color difference is only 0.16. The total computing time spent by calculating 500 intersections of mapping lines is about 1 s. Comparing with the interpolation method, the maximum color difference decreases by 2.15, computing time reduced from 10 s to 1 s and calculation speed increased nearly 10 times.关键词：gamut mapping;mapping line;CORDIC;CIE LUV120|173|3更新时间：2020-08-12
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