Luminescent characteristics of Ba_3Y_2(BO_3)_4:Eu^(3+) phosphor for white LED

The Ba3Y2（BO3）4：Eu^3＋ phosphor was synthesized using a high temperature solid-state reaction method and the luminescent characteristics were investigated. The emission spectrum exhibited one strong red emission at 613 nm, corresponding to the electric dipole 5D0-TF2 transition of Eu^3＋, under 365 nm excitation. The excitation spectrum of 613 nm indicated that the Ba3Y2（BO3）n：Eu^3＋ phosphor was effectively excited by ultraviolet （UV） （254, 365 and 400 nm） and blue （470 nm） light. The effect of Eu^3＋ concentration on the 613 nm emission of the Ba3Y2（BO3）n：Eu^3＋ phosphor was measured. The results showed that the emission intensity increased with increasing Eu^3＋ concentration, and then decreased. The CIE color coordinates of Ba3Y2（BO3）4：Eu^3＋ phosphor were x=0.641 and y=0.359 at 15 mol.% Eu^3＋.

Luminescence characteristics of Eu^(2+) activated Ca_2SiO_4,Sr_2SiO_4 and Ba_2SiO_4 phosphors for white LEDs

This paper investigates the luminescence characteristics of Eu2＋ activated Ca2SiO4, Sr2SiO4 and Ba2SiO4 phosphors. Two emission bands are assigned to the f-d transitions of Eu2＋ ions doped into two different cation sites in host lattices, and show different emission colour variation caused by substituting M2＋ cations for smaller cations. This behaviour is discussed in terms of two competing factors of the crystal field strength and covalence. These phosphors with maximum excitation of around 370 nm can be applied as a colour-tunable phosphor for light-emitting diodes （LEDs） based on ultraviolet chip/phosphor technology.

Characteristics of a large gap uniform discharge excited by DC voltage at atmospheric pressure

A large-gap uniform discharge is ignited by a coaxial dielectric barrier discharge and burns between a needle anode and a plate cathode under a low sustaining voltage by feeding with flowing argon. The basic aspects of the large-gap uniform discharge are investigated by optical and spectroscopic methods. From the discharge images, it can be found that this discharge has similar regions with glow discharge at low pressure except a plasma plume region. Light emission signals from the discharge indicate that the plasma column is invariant with time, while there are some stochastic pulses in the plasma plume region. The optical emission spectra scanning from 300 nm to 800 nm are used to calculate the excited electron temperature and vibrational temperature of the large-gap uniform discharge. It has been found that the excited electron temperature almost keeps constant and the vibrational temperature increases with increasing discharge current. Both of them decreases with increasing gas flow rate.

Preparation and luminescence characteristics of Eu^(2+) activated silicate phosphor

This paper synthesizes the Sr2SiO4：Eu^2＋ phosphor by high temperature solid-state reaction. The emission spectrum of Sr2SiO4 ： Eu^2＋ shows two bands centred at 480 and 547 nm, which agree well with the calculation values of emission spectrum, and the location of yellow emission of Sr2SiO4 ： Eu^2＋ is influenced by the Eu^2＋ concentration. The excitation spectrum for 547 nm emission has two bands at 363 and 402 nm. The emission spectrum of white light emitting diodes （w-LEDs） based on Sr2SiO4 ： Eu^2＋ phosphor ＋ InGaN LED was investigated.

Luminescence characteristics of Eu^(3+) activated borate phosphor for white light emitting diode

In this paper, the Sr3Y2 （BO3）4 ：Eu^3＋ phosphor was synthesized by high temperature solid-state reaction method and the luminescence characteristics were investigated. The emission spectrum exhibits one strong red emission at 613 nm corresponding to the electric dipole 5^Do-7^F2 transition of Eu^3＋ under 365 nm excitation, this is because Eu^3＋ substituted for Y^3＋ occupied the non-centrosymmetric position in the crystal structure of Sr3Y2（BO3）4. The excitation spectrum indicates that the phosphor can be effectively excited by ultraviolet （254 nm, 365 nm and 400 nm） and blue （470 nm） light. The effect of Eu^3＋ concentration on the red emission of Sr3Y2（BO3）4 ：Eu^3＋ was measured, the result shows that the emission intensities increase with increasing Eu^3＋ concentration, then decrease. The Commission Internationale del＇Eclairage chromaticity （x, y） of Sr3Y2（BO3）4 ：Eu^3＋ phosphor is （0.640, 0.355） at 15 mol% Eu^3＋.

Luminescence characteristics of LiCaBO_3:Tb^(3+) phosphor for white LEDs

A novel green phosphor,LiCaBO3:Tb3+,was synthesized by solid state reaction method,its luminescence characteristics were investigated,and the formation of phosphors were confirmed by X-ray powder diffraction(XRD).Its excitation band extended from 220 to 400 nm,which was coupled well with the emission of UV LED(350-410 nm).It exhibited a strong green emission located at 544 nm with chromatic coordination(0.25,0.58).The emission intensities of LiCaBO3:Tb3+ phosphor were influenced by varying Tb3+ concentratio...

Spontaneous transition of one-dimensional plasma photonic crystal's orientation in a dielectric barrier discharge

A novel one-dimensional plasma photonic crystal whose crystal orientation can change spontaneously is demonstrated using a dielectric barrier discharge with two liquid electrodes. The orientation of the plasma photonic crystal will vary from transverse to longitudinal or vary from longitudinal to transverse and then revert to longitudinal by self-adjustment, while the experimental conditions are kept fixed. The dispersion relation of these plasma photonic crystals are calculated, and the changes of the photonic band diagrams during the orientation transition are studied.

Numerical simulation of a direct current glow discharge in atmospheric pressure helium

Characteristics of a direct current （DC） discharge in atmospheric pressure helium are numerically investigated based on a one-dimensional fluid model. The results indicate that the discharge does not reach its steady state till it takes a period of time. Moreover, the required time increases and the current density of the steady state decreases with increasing the gap width. Through analyzing the spatial distributions of the electron density, the ion density and the electric field at different discharge moments, it is found that the DC discharge starts with a Townsend regime, then transits to a glow regime. In addition, the discharge operates in a normal glow mode or an abnormal glow one under different parameters, such as the gap width, the ballast resistors, and the secondary electron emission coefficients, judged by its voltage-current characteristics.

Spatio-Temporal Distribution of Individual Filaments in a Square Superlattice Pattern in Atmospheric Dielectric Barrier Discharge

Spatio-temporal distribution of individual filament in a square superlattice pattern, which consists of large and small spots （filaments）, is studied in atmospheric dielectric barrier discharges. The spatial distributions of the two discharges for individual large filament along the direction perpendicular to the electrode are estimated by the distributions of light signals along the electrode. It is found that the discharge at the rising edge of the applied voltage is with a wider column, weaker current, and longer current pulse duration in comparison with that at the falling edge

Luminescent Characteristics of LiSrBO3：Eu3＋ Phosphor for White Light Emitting Diode

LiSrBO3 ：Eu3＋ phosphor is synthesized by a high solid-state reaction method, and its luminescent characteristics are investigated. The emission and excitation spectra of LiSrBO3：Eu3＋ phosphors exhibit that the phosphors can be effectively excited by near ultraviolet （401 nm） and blue （471 nm） light, and emit 615nm red light. The effect of Eua＋ concentration on the emission spectrum of LiSrBO3：Eu3＋ phosphor is studied; the results show that the emission intensity increases with increasing Eu3＋ concentration, and then decreases because of concentration quenching. It reaches the maximum at 3mol%, and the concentration self-quenching mechanism is the dipoledipole interaction according to the Dexter theory. Under the conditions of charge compensation Li＋, Na＋ or K＋ incorporated in LiSrBO3, the luminescent intensities of LiSrBO3 ：Eua＋ phosphor are enhanced.

Optoelectronic Properties of GaN-Based Light-Emitting Diodes with Different Mesa Structures

GaN/InGaN lighting-emitting diodes with different mesa structures are studied. The current-voltage characteristics, light output power, luminous efficiency, and peak wavelength of the GaN/InGaN lighting-emitting diodes with different mesa patterns are compared. It shows that the current-voltage characteristics of the chips with more mesa areas are im- proved greatly by reducing the current crowding. With higher injection current the light output powers of GaN-based LED with more mesa areas are enhanced. And the chips with more P-electrode area have a smaller red shift and a little bit blue shift due to the reduction of the current crowding.

Improving luminescent property of SrIn_2 O_4 :Eu^(3+) by co-doped A^+ (A = Li, Na, K) or Sm^(3+)

A series of SrIn2 O4 ：Eu^3＋ phosphors are synthesized by a high temperature solid-state method, and their luminescent properties are investigated. They can be excited by 395-nm radiation, and produce red emission （619 nm）; however, they have a low absorption of near-ultraviolet light with the wavelength of 400nm–405 nm. When co-doped with A^＋ （A=Li, Na, K）, the emission intensity of SrIn2O4 ：Eu^3＋ is significantly enhanced, but its emission and excitation spectral profile is unchanged. With co-doping Sm^3＋ , not only is the emission intensity of SrIn2 O4 ：Eu^3＋ enhanced, but also the absorption is broadened and strengthened in the range of 400 nm–405nm. The effect of Sm^3＋ -doped content on the emission intensity of SrIn2O4 ：Eu^3＋ , Sm^3＋ is investigated, and the optimal Sm^3＋ content is 0.02 mol.

Self-assembled structure of cyanine dyes: J-aggregates characteristics on optical information storing microcrystals

Dye sensitization is a fundamental function for solar cell and silver halide (AgX) microcrystal to increase the optoelectronic conversion efficiency. In this paper, the spectral properties and self-assembled structure of three types of cyanine dyes, adsorbed both on (100) surface of 0.4 μm AgBr cubic crystal and (111) surface of 1.8 μm AgBr tabular crystal, were studied with combination of spectroscopy and atomic force microscopy (AFM) technique. Rectangular aggregation structure is formed on the crystal faces of (100) and (111) for both anionic and cationic dyes, while herringbone-stacking structure is formed by anionic-cationic dye, and a J-band spectrum is correspondingly detected. The photoelectron property of dye-sensitized samples was also investigated with microwave absorption and dielectric spectrum detection technology. After excited by a 355 nm fast-pulse laser, the photoelectron decay process of anionic-cationic dye sensitized sample is the fastest. This indicates that the affection of anionic-cationic dye aggregates to the photoelectron decay is the biggest, and the sensitization is more efficient.

A novel microwave absorption and dielectric spectrum detection technology in photoelectron dynamic study for solar cells

The photoelectron property is directly related to the light-energy conversion efficiency of solar cells. In this paper, the photoelectron dynamic of semiconductor was analyzed. The diffusion of electrons has influence on the dielectric function of the solar cell material. And the amplitude variance of the imaginary and real part of the dielectric function is in direct proportion to the dynamic process of free and shallow-trapped electrons. Based on the untouched detection technique, the method is present to detect the amplitude change of the microwave signal which is passing through the material whose dielectric function changes after exposure. A 35 GHz oscillator was used as a microwave source. The absorption and dispersion microwave signals, which contain the dynamic information of free and shallow-trapped electron signal, are split respectively with phase-sensitive instrument. The photoelectron character of n-type Si(100) thin film was investigated by the novel equipment, and the lifetime of different kinds of electrons with the resolution of 1 ns was obtained. The equipment can be directly used in the study of the optoelectronic conversion mechanism of solar cells.

Effects of Gas Flow Rate on the Discharge Characteristics of a DC Excited Plasma Jet

A direct current（DC） source excited plasma jet consisting of a hollow needle anode and a plate cathode has been developed to form a diffuse discharge plume in ambient air with flowing argon as the working gas.Using optical and electrical methods,the discharge characteristics are investigated for the diffuse plasma plume.Results indicate that the discharge has a pulse characteristic,under the excitation of a DC voltage.The discharge pulse corresponds to the propagation process of a plasma bullet travelling from the anode to the cathode.It is found that,with an increment of the gas flow rate,both the discharge plume length and the current peak value of the pulsed discharge decrease in the laminar flow mode,reach their minima at about1.5 L/min,and then slightly increase in the turbulent mode.However,the frequency of the pulsed discharge increases in the laminar mode with increasing the argon flow rate until the argon flow rate equals to about 1.5 L/min,and then slightly decreases in the turbulent mode.

Investigation of photoelectron action in cubic AgCl emulsion doped with formate ions

In recent years, the formate ion （HCO2^-） as a kind of hole-to-electron converter has attracted much attention of photographic researchers. The formate ions can trap photo-generated holes, eliminate or reduce the electron loss caused by electron-hole recombination in latent image formation process. Through the hole-to-electron conversion, it can also release an extra electron or electron carrier, improving photosensitivity. In this paper the microwave absorption and dielectric spectrum detection technique is used to detect the time evolution behaviour of free photoelectrons generated by 35ps laser pulses in cubic AgCl emulsions doped with formate ions. The influence of different doping conditions of formate ions on the photoelectron decay kinetics of AgC1 is analysed. It is found that when the HCO2^- content is 10^-3mol/mol Ag and the doping position is 90% the electron decay time and lifetime reach their maxima due to the efficient trap of holes by formate ions.

Elimination of Anti-spiral Waves by Local Inhomogeneity in Oscillatory Systems

Anti-spiral waves are controlled in an oscillatory system by using a local inhomogeneity. The inhomogeneity acts as a wave source, and gives rise to the propagating plane waves, tt is found that there is a critical pacemaking domain size below which no wave will be created at all. Two types of ordered waves （target waves and traveling waves） are created depending on the geometry of the local inhomogeneity. The competition between the anti-spiral waves and the ordered waves is discussed. Two different competition mechanisms were observed, which are related to the ordered waves obtained from different local inhomogeneities. It is found that traveling waves with either lower frequency or higher frequency can both eliminate the anti-spiral waves, while only the target waves with lower absolute value of frequency can eliminate the anti-spiral waves. This method also applies to outwardly rotating spiral waves. The control mechanism is intuitively explained and the control method is easily operative.

Substitution priority of Eu^(2+) in multi-cation compound Sr_(0.8)Ca_(0.2)Al_2Si_2O_8 and energy transfer

A blue phosphor was obtained by doping Eu2＋ into a multi-cation host Sro.8Cao.2Al2Si208 through high tempera- ture solid state reaction. The emission spectra show a continuous red-shift behavior from 413 nm to 435 nm with Eu2＋ concentration increasing. The substitution priority of Eu2＋ in Sro.8Cao.2AI2Si208 was investigated via x-ray diffraction （XRD） and temperature properties in detail： the Ca2＋ ions are preferentially substituted by Eu2＋at lower doping, and with the Eu2＋ concentration increasing, the probability of substitution for Sr2＋ is greater than that of replacing Ca2＋. Accord- ingly, we propose the underlying method of thermal property to determine the substitution of Eu2＋ in the multi-cation hosts. Moreover, the abnormal increase of emission intensity with increasing temperature was studied by the thermolumi- nescence spectra. The energy transfer mechanism between the Eu2＋ ions occupying different cation sites was studied by the lifetime decay curves. A series of warm white light emitting diodes were successfully fabricated using the blue phos- phors Sro.gCao.2A12Si208： Eu2＋ with commercial red phosphor （Ca Sr）SJA1N3： lu2＋ and green phosphor （Y Lu）jA15Or2 ： Ce3＋, and the luminescent efficiency can reach 45 lm/W.

Enhancement of green emission by the codoping A^+ (A= Li, Na, K) in Ca_2BO_3Cl:Tb^(3+) phosphor

Tb3＋-doped Ca2BO3C1 compounds with different charge compensation approaches are synthesized by a hightemperature solid-state reaction method, and the luminescent properties and Commission Internationale de l＇Eclairage （CIE） chromaticity coordinates are systematically characterized. Ca2BO3Cl：Tb3＋ can produce green emission under 376 nm radiation excitation. With codoped A＋ （A = Li, Na, K） as charge compensators, the relative emission intensities of Ca2BO3Cl：Tb3＋ are enhanced by about 1.61, 1.97, and 1.81 times compared with those of the direct charge balance, which is considered to be due to the effect of the difference in ion radius on the crystal field. The CIE chromaticity coordinates of Ca2BO3CI：Tb3＋, A＋ （A = Li, Na, K） are （0.335, 0.584）, （0.335, 0.585）, and （0.335, 0.585）, corresponding to the hues of green. Therefore, A＋ （A = Li, Na, K） may be the optimal charge compensator for Ca2BO3Cl：Tb3＋.

Using fuzzy cognitive maps to model performance measurement system of Internet-based supply chain

Fuzzy cognitive maps （FCM） is a well-established artificial intelligence technique, which can be effectively applied in the domains of performance measurement, decision making and other management science. FCM can be a useful tool in a group decision-making environment by using scientifically integrated expert knowledge. The theories of FCM and balance scorecard （BSC） both emphasize cause-and-effect relationships among indicators in a complex system, but few reports have been published addressing the combined application of these two techniques. In this paper we propose a FCM simulation model for the sample performance measurement system of Intemet-based supply chain, which is constructed by BSC theory. We gave examples to explain how FCM can be adapted to execute the causal mechanism of BSC, and also how FCM can support group decision-making and forecasting in performance measurement.