• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.10 no.4
• /
• pp.302-308
• /
• 2000

Stable amorphous calcium carbonate were synthesized from the serial work for the synthetic conditions such as concentration of solution, reaction temperature, aging time and pH of mother liquor. By using this as a precusor, calcite, aragonite and vaterite crystal particles were obtained in the water from adequate crystallization conditions. Furthermore, characterization for flourescence were performed by using crystals which were crystallized from the Sn dopped amorphous calcium carbonate. Calcite showed the most intensive emission and the center of emission wavelength was 464 nm with pure blue color. Calcite is expected to be used as phosphor for flourescent lamp because the maximum emission intensity was obtained from the excitation with 255 nm wavelength.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2000.07a
• /
• pp.303-307
• /
• 2000

The crystal structure of ZnS fabricated by gas-liquid phase reaction was obtained by XRD and refined by RIETAN near R$_{wp}$ factor 10%. The increasement of HCP phase depended on extra H$_2$S gas and the lattice parameter and crystalline size changed by the relative ratio of multiphase. Using ZnS of the different multiphase ratio and crystalline size, sintered ZnS:Cu, Al green phosphor and the CL property resulted optimum luminescence in the range of 91~94% and 150~190$\AA$, respectably, FCC/HCP ratio and crystalline size. As changing of structure ratio, the reason of different luminescence property is now studying. As well as, after XRD pattern of TiO$_2$powder fitted by RIETAN and the structure factor using MEED method simulated about each atom of (002) plane. Additionally, we proposed RIETAN and MEED were the methods of the study of luminescence mechanism for many phosphor materials.s.

• Current Applied Physics
• /
• v.18 no.11
• /
• pp.1225-1229
• /
• 2018

In this paper, we investigated the electronic structures and defect states of $SrLaMgTaO_6$ (SLMTO) double perovskite structures by using resonant inelastic x-ray scattering. Recently, $Eu^{3+}$ doped SLMTO red phosphors have been vigorously investigated due to their higher red emission efficiency compared to commercial white light emitting diodes (W-LED). However, a comprehensive understanding on the electronic structures and defect states of host SLMTO compounds, which are specifically related to the W-LED and photoluminescence (PL), is far from complete. Here, we found that the PL spectra of SLMTO powder compounds sintered at a higher temperature, $1400^{\circ}C$, were weaker in the blue emission regions (at around 400 nm) and became enhanced in near infrared (NIR) regions compared to those sintered at $1200^{\circ}C$. To elucidate the difference of the PL spectra, we performed resonant inelastic x-ray spectroscopy (RIXS) at Ta L-edge. Our RIXS result implies that the microscopic origin of different PL spectra is not relevant to the Ta-related defects and oxygen vacancies.

• Journal of Sensor Science and Technology
• /
• v.1 no.1
• /
• pp.59-66
• /
• 1992

To develop the highly sensitive TLD radiation sensors, $BaSO_{4}$ : Eu-PTFE TLDs are fabricated by polymerizing the PTFE(polytetrafluoroethylene) with $BaSO_{4}$ : Eu TL phosphors. The $BaSO_{4}$ : Eu TL phosphors having the highest sensitivity of $X/{\gamma}$-rays are obtained by sintering at $1000^{\circ}C$ in $N_{2}$ atmosphere a mixture of $BaSO_{4}$ powder with 1mol% Eu($Eu_{2}O_{3}$), 6mol% $NH_{4}Cl$ and 5mol% $(NH_{4})_{2}SO_{4}$ which were co-precipitated in dilute sulfuric acid and then dried. The activation energy, frequency factor and kinetic order of $BaSO_{4}$ : Eu TL phosphor are 1.17eV, $3.6{\times}10^{11}/sec$ and 1.25, respectively. And the spectral peak of $BaSO_{4}$ : Eu is about 425nm. The optimum TL Phosphor content and thickness of the $BaSO_{4}$ : Eu-PTFE TLD are 40wt% and $105.7mg/cm^{2}$. The optimum polymerization temperature and time for fabrication of $BaSO_{4}$ : Eu-PTFE TLDs are $380^{\circ}C$ and 2 hours in air, respectively. The linear dose range to ${\gamma}$ rays is 0.01-20Gy and fading rate is about 10%/60hours.

• Journal of the Korean Society of Radiology
• /
• v.9 no.3
• /
• pp.169-174
• /
• 2015

$LiGd_9(SiO_4)_6O_2:Ce^{3+}$ phosphors were synthesized by solid-state reaction method. The structural characteristic was investigated by X-ray powder diffraction analysis. The emission and excitation spectra of the $Ce^{3+}$ ions doped $LiGd_9(SiO_4)_6O_2$ phosphors were obtained under the UV excitation. The emission spectra of $LiGd_9(SiO_4)_6O_2:Ce^{3+}$ shows the band at 410 nm corresponding to the $^2F_{5/2}$ and $^2F_{7/2}$ states of $Ce^{3+}$. The red shift of $Ce^{3+}$ emission is found as the $Ce^{3+}$ concentration increases, which could be explained by the change in crystal-field symmetry and strength with increasing $Ce^{3+}$ concentration. Fluorescence decay time of $Ce^{3+}$ was about 20 ns. When the concentration of $Ce^{3+}$ increases life time was slightly reduced.

• Journal of the Korean Ceramic Society
• /
• v.39 no.11
• /
• pp.1023-1027
• /
• 2002

In this paper, we have prepared phase-pure $SrTiO_3:\;Pr^{3+}$ phosphor powder by Supercritical Fluid Mixing using $Sr(OH)_2{\cdot}8H_2O$ and $TiO_2$ powders as starting materials. Its luminescent properties were investigated in comparison with $SrTiO_3:\;Pr^{3+}$ powders prepared by solid-state method with conventional mixing. $SrTiO_3:\;Pr^{3+}$ phosphor powders by Supercritical Fluid Mixing have spherical shapes and narrow particle size distribution. We have investigated the luminescent properties of $SrTiO_3:\;Pr^{3+}$ phosphor using $Al^{3+}$ and $Ga^{3+}$ as sensitizer.

• Korean Journal of Materials Research
• /
• v.11 no.8
• /
• pp.636-640
• /
• 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
• /
• v.11 no.8
• /
• pp.363-363
• /
• 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
• /
• v.47 no.2
• /
• pp.122-126
• /
• 2010

In this article photoluminescence of the $Al_2O_3:xCr_2O_3$ solid solutions prepared by solid state reaction method are represented. The effect of $Cr_2O_3$-activator concentration and heat treatment time on the PL characteristics have been discussed in conjunction with microstructure of phosphor samples. The $Al_2O_3:xCr_2O_3$ phosphors show the highest PL intensity at x=0.003 mole when the samples are reacted at $1600^{\circ}C$ for 5 h. The PL emission and absorption spectra show the maximum peaks at 698 nm and at 398 nm respectively. The CIE color coordinate is (x=0.646, y=0.316) at 0.003 mole $Cr_2O_3$, which value is very close to the NTSC coordinate of red color. This characteristic feature of $Al_2O_3:xCr_2O_3$ has been applied for an additive to improve the color characteristic of other red phosphor $LiEuW_2O_8$ which has a relatively poor color purity with an emission peak centered at 615 nm and with a CIE coordinate (x=0.530, y=0.280). The $Al_2O_3:0.003Cr_2O_3$ phosphor has been mixed with the $LiEuW_2O_8$ phosphor powder and the PL characteristics and CIE color coordinates are characterized. The $Al_2O_3:xCr_2O_3$ phosphor was found effective for improving the CRI (color rendering index) of $LiEuW_2O_8$ phosphor.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.13 no.3
• /
• pp.111-116
• /
• 2003

The red emitting phosphors for low voltage cathode luminescent, fine $(Y,Gd)_2O_2$S : Eu powders were synthesized and investigated the effect of $Gd^{3+}$as sensitizer at variety of sintering temperature. The highly intense emission line of $(Y,Gd)_2O_2$S : Eu at 627 nm is attributed in the transition from $^5D_o to ^7F_2$ energy levels. It showed the maximum value at the doping level of 5 mole% of $Gd^{3+}$at $950^{\circ}C$ of sintering temperature and then, it was degraded rapidly. The mean particle size of $(Y,Gd)_2O_2$S : Eu was obtained around 1 fm and the cathode luminescent properties of (Y,Gd)$_2$O$_2$S : Eu were better than those of $(Y,Gd)_2O_2$S : Eu.