• Proceedings of the Korean Ceranic Society Conference
• /
• 2003.10a
• /
• pp.144.1-144
• /
• 2003

• Korean Journal of Materials Research
• /
• v.23 no.1
• /
• pp.31-34
• /
• 2013

Trivalent cerium-ion-doped $Y_3(Al,\;Ga)_5O_{12}$ nanoparticle phosphor nanoparticles were synthesized using the reverse micelle process. The Ce doped $Y_3(Al,\;Ga)_5O_{12}$ particles were obtained from nitrate solutions dispersed in the nanosized aqueous domains of a micro emulsion consisting of cyclohexane as the oil phase and poly(oxyethylene) nonylphenyl ether (Igepal CO-520) as the non-ionic surfactant. The crystallinity, morphology, and thermal properties of the synthesized $Y_3(Al,\;Ga)_5O_{12}:Ce^{3+}$ powders were characterized by thermogravimetry-differential thermal analysis (TGA-DTA), X-ray diffraction analysis (XRD), scanning electron microscopy (SEM), and transmission electron microscopy. The crystallinity, morphology, and chemical states of the ions were characterized; the photo-physical properties were studied by taking absorption, excitation, and emission spectra for various concentrations of cerium. The photo physical properties of the synthesized $Y_3(Al,\;Ga)_5O_{12}:Ce^{3+}$ powders were studied by taking the excitation and emission spectra for various concentrations of cerium. The average particle size of the synthesized YAG powders was below $1{\mu}m$. Excitation spectra of the $Y_3Al_5O_{12}$ and $Y_3Al_{3.97}Ga_{1.03}O_{12}$ samples were 485 nm and 475 nm, respectively. The emission spectra of the $Y_3Al_5O_{12}$ and $Y_3Al_{3.97}Ga_{1.03}O_{12}$ were around 560 nm and 545 nm, respectively. $Y_3(Al,\;Ga)_5O_{12}:Ce^{3+}$ is a red-emitting phosphor; it has a high efficiency for operation under near UV excitation, and may be a promising candidate for photonic applications.

• Korean Journal of Crystallography
• /
• v.5 no.2
• /
• pp.51-66
• /
• 1994

Y3Al5O2 and Nd: Y3Al5012 single crystals were grown by Czochralskl technique. The effectt of pulling rate rotation rate, and doping level of Nd3+ ion on the crystal quality were studied Various types of defects were analysed by photo-elastic effect and chemical etching method Finally, spectroscopic and laser poputies of grown crystal were measured. Optirmum pulling rate for good quality was dependant on the doping level of Nd3+ ion. It was found that the suitable pulling rates for pure Y3Al5O12 for 3.0∼3.5 a/o Nd3+ ion doped Y3Al5012 and for more than 40 a/o Nd3+ ion doped Y3Al5012 were 2∼4mm/hr, 0.6∼0.5mm/hr, and less than 0.4mm/hr respectively. Solid-liquid interface was convex at the rotation rate of 27∼60rpm, and concave at the rotation rate of 80∼100rpm. Growth axis was confired to <111> direction and lattice parameter was measured to 12.017A. Core (211) facets,striations, inclusions of metal particles, dislocations and optical inhonngeneities were detected. Four level laser transition of Nd3+ion in YIAls012 single crystal were identified by the spectroscopic measurements. Laser rod with tam diameter and 63mm length was fabricated from grown Nd3+ Y3Al5012 sin91e crystals. 1.8lJ of lasing threshould and 0.49% of soope efficiency were measured by the Pulsed laser action.

• Korean Journal of Materials Research
• /
• v.21 no.11
• /
• pp.604-610
• /
• 2011

The effect of $BaF_2$ flux in $Y_3Al_5O_{12}:Ce^{3+}$(YAG:Ce) formation was investigated. Phase transformation of $Y_3Al_5O_{12}$(YAG) was characterized by using XRD, SEM, and TEM-EDS, and it was revealed that the sequential formation of the $Y_4Al_2O_9$(YAM), $YAlO_3$(YAP) and $Y_3Al_5O_{12}$(YAG) in the temperature range of 1000-1500$^{\circ}C$. Single phase of YAG was revealed from 1300$^{\circ}C$. In order to find out the effect of $BaF_2$ flux, three modeling experiments between starting materials (1.5$Al_2O_3$-2.5$Y_2O_3$, $Y_2O_3$-$BaF_2$, and $Al_2O_3$-$BaF_2$) were done. These modeling experiments showed that the nucleation process occurs via the dissolution-precipitation mechanism, whereas the grain growth process is controlled via the liquid-phase diffusion route. YAG:Ce phosphor particles prepared using a proposed technique exhibit a spherical shape, high crystallinity, and an emission intensity. According to the experimental results conducted in this investigation, 5% of $BaF_2$ was the best concentration for physical, chemical and optical properties of $Y_3Al_5O_{12}:Ce^{3+}$(YAG:Ce) that is approximately 10-15% greater than that of commercial phosphor powder.

• Korean Journal of Materials Research
• /
• v.32 no.10
• /
• pp.425-428
• /
• 2022

In this study, Y₃Al₅O₁₂:Eu³⁺ red phosphors were synthesized at different temperatures using a solid state reaction method. The crystal structures, surface and optical properties of the Y₃Al₅O₁₂:Eu³⁺ red phosphors were investigated using X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), and photoluminescence (PL) analyses. From XRD results, the crystal structure of the Y₃Al₅O₁₂:Eu³⁺ red phosphors was determined to be cubic. The maximum emission spectra were observed for the Y₃Al₅O₁₂:Eu³⁺ red phosphor prepared by annealing for 4h at 1,700 ℃. The 565~590 nm photoluminescent spectra of the Y₃Al₅O₁₂:Eu³⁺ red phosphors is associated with the ⁵D₀ → ⁷F₂ magnetic dipole transition of the Eu³⁺ ions. The intensity of the photoluminescent spectra in the red phosphors is more dominant for the magnetic dipole transition than the electric dipole transition with increasing annealing temperature. The International Commission on Illumination (CIE) coordinates of Y₃Al₅O₁₂:Eu³⁺ red phosphors prepared by 1,700 ℃ annealing temperature are X = 0.5994, Y = 0.3647.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
• /
• 2006.11a
• /
• pp.169-172
• /
• 2006

In the present work, silicon nitride was fabricated with $Y_3Al_5O_{12}$ as sintering additive and its mechanical properties were investigated. Silicon nitride with 3, 5, 7wt% of $Y_3Al_5O_{12}$ was prepared and sintered by a Hot Pressing (HP) technique at 1750, $1800^{\circ}C$ for 2 hours. The Process was fulfilled under different process pressures of 30, 45MPa respectively. Mechanical properties (density, strength, hardness, fracture toughness) were investigated as a function of $Y_3Al_5O_{12}$ contents in $Si_3N_4$. $Si_3N_4-Y_3Al_5O_{12}$ ceramics showed similar mechanical properties compared with $Si_3N_4-Y_2O_3-Al_2O_3$ ceramics. But its high temperature strength was higher than $Si_3N_4-Y_2O_3-Al_2O_3$ceramics considerably.

• Journal of Ocean Engineering and Technology
• /
• v.21 no.6
• /
• pp.95-100
• /
• 2007

In the present work, silicon nitride was fabricated with $Y_3Al_5O_{12}$ as a sintering additive and its mechanical properties were investigated. Silicon nitride with 3, 5, and 7wt% of $Y_3Al_5O_{12}$ was prepared and sintered by a Hot Pressing (HP) technique at 1750 and $1800^{\circ}C$ for 2 h. The process was performed under different process pressures of 30 and 45 MPa. Mechanical properties (density, strength, hardness, and fracture toughness) were investigated as a function of the $Y_3Al_5O_{12}$ content in $Si_3N_4$. $Si_3N_4\;-Y_3Al_5O_{12}$ ceramics showing similar mechanical properties compared with $Si_3N_4-Y_2O_3-Al_2O_3$ ceramics. But its high temperature strength was considerably higher than that of $Si_3N_4-Y_2O_3-Al_2O_3$ ceramics.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.7 no.2
• /
• pp.244-252
• /
• 1997

The pseudo-spinel type solid solution, $LiAl_{2.5}/Fe_{2.5}O_8$ was prepared by reaction of $LiCO_3, Al_2O_3, Fe_2O_3$ mixture at 1620K, which can be used for cathode material in lithium batteries. Its structure was investigated by Rietveld profile-analysis of XRD in detail. The space group of solid solution is $P4_3$32(a=8.1293$\AA$) and the final residual index of structure refinement was about 5%. Cations $Al^{3+}, Fe^{3+}$ are located at both tetra- and octahedral-coordination and $Li^+$ ions are occupied in the octahedral 4b-, 12d-site of the inverse spinel.

• Journal of the Korean Chemical Society
• /
• v.46 no.4
• /
• pp.336-345
• /
• 2002

In this study, we have screened $Eu^{3+}$- and $Tb^{3+}$-activated candidate phosphors for PDP in the sys-tems of CaO-Gd$_2$O$_3$-Al$_2$O$_3$ by combinatorial chemistry and investigated the synthetic temperature, optimum com-position and luminescent properties about the candidate phosphors. To construct the emission intensity library by VUV PL, we have synthesized 210 different compositional samples using a polymerized-complex method. Good luminescent samples were identified by X-ray diffraction method. $Ca_$\alpha$$G$d_{0.95-$\alpha$-$\beta$}Al_$\beta$O_$\delta$$ : Eu(0.02< $\alpha$+$\beta$ <0.04) phos-phors screened as a red phosphor have good color purity than commercial phosphor. In the candidate phosphors of CaGdAl$_3O_7$ : Tb, Ca$Al_{12}O_{19}$ : Tb, Gd$_4$Al$_2O_9$ : Tb, and Gd$_3Al_5O_{12}$ : Tb CaGdAl$_3O_7$ : Tb, and Ca$Al_{12}O_{19}$ : Tb have shorter decay time than commercial phosphor.

• Korean Journal of Materials Research
• /
• v.11 no.12
• /
• pp.1080-1085
• /
• 2001

Dielectric properties and leakage current characteristics of 100 nm-thick $Ta_2O_5/Al_2O_3$multilayer thin films, which were fabricated by reactive sputtering of$Al_2O_3$and$Ta_2O_5$ successively on top of each other for total 9 layers, have been investigated with variation of the$Al_2O_3$content$(i.e,\;Ta_2O_5/Al_2O_3 \;thickness\;ratio)$.$Ta_2O_5/Al_2O_3$films were amorphous regardless of the$Al_2O_3$content. With increasing the$Al_2O_3$content from 0% to 100%, refractive index of the $Ta_2O_5/Al_2O_3$films decreased linearly from 2.03 to 1.56 and dielectric constant was lowered from 23.9 to 7.7 Variation of the dielectric constant with the$Al_2O_3$content was in good agreement with the behavior that was obtained by assuming parallel capacitors of$Al_2O_3$and Ta_2O_5$. Leakage current characteristics of $Ta_2O_5/Al_2O_3$ multilayer films were superior to those of $Ta_2O_5$ and$Al_2O_3$films. $Ta_2O_5/Al_2O_3$ films of 5% and 10%$Al_2O_3$content exhibited excellent leakage current densities which were lower than $10^{-7} A/cm^2$ at 1MV/cm.