• Korean Chemical Engineering Research
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• v.44 no.6
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• pp.609-613
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• 2006

Ba2-xSrxSiO4:Eu2+ phosphor particles with the high photoluminescence (PL) intensity under long wavelength ultraviolet (UV) were prepared by spray pyrolysis. The photoluminescence, morphological and crystalline characteristics of $Ba_{2-x.}Sr_{x.}SiO_4:Eu^{2+}$ phosphor particles prepared by spray pyrolysis were investigated. $Ba_{2-x.}Sr_{x.}SiO_4:Eu^{2+}$ phosphor particles prepared by spray pyrolysis had various colors from bluish green to yellow by changing the ratio of barium and strontium of the host material. In case of x=0, the main emission peak of $Ba_2SiO_4:Eu^{2+}$ phosphor was 500 nm. In case of x=2, the main emission peak of $Sr_2SiO_4:Eu^{2+}$ phosphor was 554nm. $Ba_{2-x.}Sr_{x.}SiO_4:Eu^{2+}$ phosphor particles obtained by spray pyrolysis had spherical shape and hollow structure. On the other hand, the post-treated $Ba_{2-x.}Sr_{x.}SiO_4:Eu^{2+}$ phosphor particles had large size and irregular shape. The $Ba_{1.488}Sr_{0.5}SiO_4:Eu_{0.012}{^{2+}}$ phosphor particles had the maximum PL intensity after post-treatment at temperature of $1300^{\circ}C$ for 3h under reduction atmosphere.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.328-328
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• 2007

Large area matrix-addressed image detectors are a recent technology for x-ray imaging with medical diagnostic and other applications. The imaging properties of x-ray pixel detectors depend on the quantum efficiency of x-rays, the generated signal of each x-ray photon and the distribution of the generated signal between pixels. In a phosphor coated detector the light signal is generated by electrons captured in the phosphor screen. In our study we simulated the lateral spread distributions for phosphor coupled detector by Monte Carlo simulations. Most simulations of such detectors simplify the setup by only taking the conversion layer into account neglecting behind. The Monte Carlo code MCNPX has been used to simulate the complete interaction and subsequent charge transport of x-ray radiation. This has allowed the analysis of charge sharing between pixel elements as an important limited factor of digital x-ray imaging system. The parameters are determined by lateral distribution of x-ray photons and x-ray induced electrons. The primary purpose of this study was to develop a design tool for the evaluation of geometry factor in the phosphor coupled optical imaging detector. In order to evaluate the spatial resolution for different phosphor material, phosphor geometry we have developed a simulation code. The developed code calculates the energy absorption and spatial distribution based on both the signal from the scintillating layer and the signal from direct detection of x-ray in the detector. We show that internal scattering contributes to the so-called spatial resolution drop of the image detector. Results from the simulation of spatial distribution in a phosphor pixel detector are presented. The spatial resolution can be increased by optimizing pixel size and phosphor thickness.

• The Journal of the Convergence on Culture Technology
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• v.9 no.5
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• pp.523-528
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• 2023

The applicability as a material to improve solar cell performance was reviewed by synthesizing a phosphor that emits red wavelengths by a liquid synthesis method using a metal salt aqueous solution and a polymer medium as a starting material. An aqueous solution was prepared using nitrate of metals such as Ca, Zn, Al, and Eu, and a precursor impregnated with starch, a natural polymer, was sintered to synthesize CaZnAlO:Eu phosphor powder. The surface structure and composition analysis of the synthesized CaZnAlO:Eu phosphor powder were analyzed by scanning electron microscope(SEM) and energy-dispersed X-ray spectroscopy(EDS). The crystal structure of CaZnAlO:Eu phosphor particles was analyzed by an X-ray diffraction analyzer (XRD). As a result of measuring the photoluminescence(PL) characteristics of the phosphor, it was confirmed that a red phosphor with a light emitting wavelength of 650-780nm was successfully synthesized. According to SEM and EDS analysis, the synthesized Ca₁₄Zn₆Al_9.93O₃₅:Eu³⁺_0.07 phosphor powder has a uniform particle size, and Eu ions used as an activator are present. The synthesized CZA:Eu³⁺ phosphor can be used as a material that can increase the light absorption efficiency of the solar cell by converting ultraviolet or visible light down conversion into a wavelength in the near-infrared region.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.30 no.2
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• pp.73-77
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• 2020

In this study, phosphor ceramics were fabricated, and optical properties were analyzed for application to nextgeneration automotive laser headlamps by using a spherical YAG : Ce phosphor with a garnet structure synthesized based on the spray drying method. The thickness of phosphor ceramic using spherical YAG : Ce phosphor was obtained with 100 ㎛, 150 ㎛, and 200 ㎛ to investigate the effect of thickness on optical properties such as light conversion efficiency, heat dissipation, luminance and color temperature. The results of this study are expected to play a significant role in the manufacturing process for the fabrication of phosphor ceramic by solving issues such as the high cost and low yield in the conventional liquid method to manufacture YAG : Ce nano fluorescent materials.

• Current Photovoltaic Research
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• v.4 no.1
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• pp.25-29
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• 2016

$Eu^{3+}$-activated $MgMoO_4$ phosphor thin films were grown at $400^{\circ}C$ on quartz substrates by radio-frequency magnetron sputter deposition from a 15 mol% Eu-doped $MgMoO_4$ target. After the deposition, the phosphor thin films were annealed at several temperatures for 30 min in air. The influence of thermal annealing temperature on the structural and optical properties of $MgMoO_4:Eu^{3+}$ phosphor thin films was investigated by using X-ray diffraction (XRD), photoluminescence (PL), and ultraviolet-visible spectrophotometry. The transmittance, optical band gap, and intensities of the luminescence and excitation spectra of the thin films were found to depend on the thermal annealing temperature. The XRD patterns indicated that all the thin films had a monoclinic structure with a main (220) diffraction peak. The highest average transmittance of 91.3% in the wavelength range of 320~1100 nm was obtained for the phosphor thin film annealed at $800^{\circ}C$. At this annealing temperature the optical band gap energy was estimated as 4.83 eV. The emission and excitation spectra exhibited that the $MgMoO_4:Eu^{3+}$ phosphor thin films could be effectively excited by near ultraviolet (281 nm) light, and emitted the dominant 614 nm red light. The results show that increasing RTA temperature can enhance $Eu^{3+}$ emission and excitation intensity.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.31 no.5
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• pp.324-329
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• 2018

Red phosphor in glasses (PiGs) for automotive light-emitting diode (LED) applications were fabricated with 620-nm $CaAlSiN_3:Eu^{2+}$ phosphor and Pb-free silicate glass. PiGs were synthesized and mounted on high-power blue LED to make a monochromatic red LED. PiGs were simple mixtures of red phosphor and transparent glass powder. After being fabricated with uniaxial press and CIP at 300 MPa for 20 min, the green bodies were thermally treated at $550^{\circ}C$ for 30 min to produce high dense PiGs. As the phosphor content increased, the density of the sintered body decreased and PiGs containing 30% phosphor had a full sintered density. Changes in photoluminescence spectra and color coordination were studied by varying the thickness of plates that were mounted after optical polishing. As a result of the optical spectrum and color coordinates, PiG plate with $210{\mu}m$ thickness showed a color purity of 99.7%. In order to evaluate the thermal stability, the thermal quenching characteristics were measured at temperatures of $30{\sim}150^{\circ}C$. The results showed that the red PIG plates were 30% more thermally stable compared to the AlGaInP red chip.

• 한국정보디스플레이학회:학술대회논문집
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• 2004.08a
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• pp.575-578
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• 2004

The charging tendency of $Zn_2SiO_4:Mn^{2+}$ phosphor surface was modified in order to improve discharging characteristic of green cell in an ac-plasma display panel (ac-PDP). The Zinc-silicate ($Zn_2SiO_4:Mn^{2+}$) green-emitting phosphor was coated with magnesium oxide(MgO), which is viable to have positive charge on the surface. After fabricating the green cell with MgO-coated $Zn_2SiO_4:Mn^{2+}$, the electrical and optical properties in the cell were examined. It was found that the dynamic voltage margin could be increased while the address time was reduced. It may be ascribed to the change of charging tendency of $Zn_2SiO_4:Mn^{2+}$ phosphor by MgO coating, which makes it possible to stable wall-charge accumulation. When $Zn_2SiO_4:Mn^{2+}$ phosphor was coated with 1.3wt%-MgO, the address time was reduced 1.2 ${\mu}s$ and the address voltage lowered 25 V without any misfiring problem, compared to those of typical $Zn_2SiO_4:Mn^{2+}$ phosphor layer. The luminescence intensity of green cell using MgO-coated phosphor layer was also improved by 10%.

• Korean Journal of Materials Research
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• v.11 no.8
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• pp.636-640
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• 2001

In order to improve the optical Performance of green emitting phosphor for plasma display panel (PDP) application, the wet chemical method for preparing $Zn_{2-x}$ $SiO_4$:xMn (xi=0.02. 0.08) phosphor was designed. The spherical phosphor particles were obtained and the size can be between 0.5$\mu\textrm{m}$ and 2$\mu\textrm{m}$. The formation of phosphor, which had the willemite structure, was completed at relatively low temperature of 108$0^{\circ}C$. Also, photoluminescence Properties of the phosphors prepared were investigated under vacuum ultraviolet excitation. In particular, the emission intensity of Zn$_2$SiO$_4$:0.08Mn phosphor having the 1$\mu\textrm{m}$ of particle size was higher than that of commercial phosphor by 40%. The decay time of zinc silicate powder prepared as containing 8 mole% of manganese has been measured as 7.8ms.

• Korean Journal of Materials Research
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• v.11 no.8
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• pp.363-363
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• 2001

In order to improve the optical Performance of green emitting phosphor for plasma display panel (PDP) application, the wet chemical method for preparing $Zn_{2-x}$ $SiO_4$:xMn (xi=0.02. 0.08) phosphor was designed. The spherical phosphor particles were obtained and the size can be between 0.5$\mu\textrm{m}$ and 2$\mu\textrm{m}$. The formation of phosphor, which had the willemite structure, was completed at relatively low temperature of 108$0^{\circ}C$. Also, photoluminescence Properties of the phosphors prepared were investigated under vacuum ultraviolet excitation. In particular, the emission intensity of Zn$_2$SiO$_4$:0.08Mn phosphor having the 1$\mu\textrm{m}$ of particle size was higher than that of commercial phosphor by 40%. The decay time of zinc silicate powder prepared as containing 8 mole% of manganese has been measured as 7.8ms.

• Journal of the Korean Ceramic Society
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• v.43 no.3 s.286
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• pp.169-172
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• 2006

We have synthesized a $Eu^{2+}-activated\;{(Sr,Ba)}_2SiO_4$ yellow phosphor and investigated the development of blue LEDs by combining the phosphor with a InGaN blue LED chip (${\lambda}_{em}$=405 nm). The InGaN-based ${(Sr,Ba)}_2SiO_{4}:Eu$ LED lamp shows two bands at 405 nm and 550 nm. The 405 nm emission band is due to a radiative recombination from a InGaN active layer. This 405 nm emission was used as an optical transition of the ${(Sr,Ba)}_2SiO_{4}:Eu$ phosphor. The 550 nm emission band is ascribed to a radiative recombination of $Eu^{2+}$ impurity ions in the ${(Sr,Ba)}_2SiO_4$ host matrix. In the preparation of UV Yellow LED Lamp with ${(Sr,Ba)}_2SiO_{4}:Eu$ yellow phosphor, the highest luminescence efficiency was obtained at the epoxy-to-yellow phosphor ratio of 1:0.45. At this ratio, the CIE chromaticity was x=0.4097 and y=0.5488.