• Journal of the Korean Crystal Growth and Crystal Technology
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• v.25 no.1
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• pp.1-5
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• 2015

For the special usage, the effort of developing AlN single crystals has been very hot in the world. The AlN-base UV LEDs are used on the field of sterilization, purification, curing and analyzing, which can advance human's living and medical processes etc.. AlN single crystals were grown by the PVT (Physical vapor transport) method. On the growing process, carbon crucibles with three different types such as normal size, taller than normal and wider than normal were used for comparison. The processing temperature was in the range of $1900{\sim}2100^{\circ}C$ and ambient pressure was 200~1 Torr. When the taller crucible was used, the sublimation mass was greater than normal dimension one but the best condition of growth changes widely. However the wider one gave much sublimation mass and growing condition was more stable than normal dimension. On limited growing furnace system, the changes of crucible dimension of PVT method provide the change of best condition for growth rate, as-grown crystal quality and growth condition stability.

• Journal of the Korean Solar Energy Society
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• v.38 no.1
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• pp.25-36
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• 2018

The stoichiometric mixture of evaporating materials for the $CaAl_2Se_4$: Co single crystal thin film was prepared from horizontal furnace. Using extrapolation method of X-ray diffraction patterns for the polycrystal $CaAl_2Se_4$, it was found orthorhomic structure whose lattice constant $a_0$, $b_0$ and $c_0$ were 6.4818, $11.1310{\AA}$ and $11.2443{\AA}$, respectively. To obtain the $CaAl_2Se_4$: Co single crystal thin film, $CaAl_2Se_4$: Co mixed crystal was deposited on throughly etched Si (100) by the HWE (Hot Wall Epitaxy) system. The source and substrate temperature were $600^{\circ}C$ and $440^{\circ}C$ respectively. The crystalline structure of $CaAl_2Se_4$: Co single crystal thin film was investigated by the double crystal X-ray diffraction (DCXD). Hall effect on this sample was measured by the method of Van der Pauw and studied on carrier density and mobility depending on temperature. From Hall data, the mobility was likely to be decreased by impurity scattering in the temperature range 30 K to 100 K and by lattice scattering in the temperature range 100 K to 293 K. The temperature dependence of the energy band gap of the $CaAl_2Se_4$: Co obtained from the absorption spectra was well described by the Varshni's relation, $E_g(T)=3.8239eV-(4.9823{\times}10^{-3}eV/K)T_2/(T+559K)$. The open-circuit voltage, short current density, fill factor, and conversion efficiency of $p-Si/p-CaAl_2Se_4$: Co heterojunction solar cells under $80mW/cm^2$ illumination were found to be 0.42 V, $25.3mA/cm^2$, 0.75 and 9.96%, respectively.

• Journal of the Korean Chemical Society
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• v.55 no.4
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• pp.570-574
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• 2011

Large colorless single crystals of analcime with diameters up to 0.20 mm have been synthesized from gels with the composition of $3.00SiO_2$ : $1.50NaAlO_2$ : 8.02NaOH : $454H_2O$ : 5.00TEA. The fully $Na^+$-exchanged analcime have been prepared with aqueous 0.1 M NaCl (pH adjusted from 6 to 11 by dropwise addition of NaOH). The single-crystal structure of hydrated $|Na_{0.94}(H_2O)|[Si_{2.06}Al_{0.94}O_6]$-ANA per unit cell, a=13.703(3) ${\AA}$, has been determined by single-crystal X-ray diffraction technique in the orthorhombic space group Ibca at 294 K. The structure was refined using all intenties to the final error indices (using only the 1,446 reflections for which $F_o$ > $4{\sigma}(F_o))R_1/wR_2$ = 0.054/0.143. About 15 $Na^+$ ions are located at three nonequivalent positions and octahedrally coordinated. The chemical composition is $Na_{0.94}(H_2O)Si_{2.06}Al_{0.94}O_6$. The Si/Al ratio of synthetic analcime is 2.19 determined by the occupations of cations, 14.79, in the single-crystal determination work.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 1996.06a
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• pp.519-521
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• 1996

Emerald (3BeO.Al2O3.6SiO2 : Cr3+) single crystals were crystals were grown by reflux method of temperature gradient in the flux solution of Li2O-MoO3-V2O5 system. The composition of flux materials were 3 mole ratio of MoO3-V2O5/Li2O, subtituted 0.2 mole% of K2O, Na2O, Nb2O5 etc to Li2O content, solved 10-15% of beryl to flux quantity and doped 1% of Cr2O3 to emerald amount. Those of mixing were melted at 110$0^{\circ}C$ in Pt containers of the 3 zone furnace of melt-growth-return to circulate continniously, specially it has been grown large emerald single crystal when thermal fluctuation was treated for 2hrs of once time a day at 1050-95$0^{\circ}C$ in growth zone, substitutional solid solution effect of Cr+3 ion for Al+3 to the growth of emerald single crystal was good. Emerald single crystals were c(0001) hexagonal crystal face of preferencial growth direction and m(1010) post side. When it had been durated for 5 months emerald single crystals of the firet size of 0.6mm thickness of seed crystal were grown 32$\times$65mm(c x m) of maximum size and 6.2mm thickness.

• Journal of the Semiconductor & Display Technology
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• v.17 no.4
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• pp.37-41
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• 2018

$Y_3A_{l5}O_{12}:Ce^{3+},Pr^{3+}$ single crystal phosphor was prepared by floating zone method. single crystal was confirmed to have a Ia-3d (230) space group of cubic structure and showed regular morphology. The optical properties, single crystal exhibited a emission band from green, yellow wide wavelength and 610nm, 640nm red wavelength vicinity. The luminance maintenance rate was decreased by phonon with increasing temperature, but high luminance is maintained more than powder phosphor. In addition, $Y_3A_{l5}O_{12}:Ce^{3+},Pr^{3+}$ single crystal phosphor was applied to a high power blue laser diode, we implemented high power white laser lightings. and it was confirmed that thermal properties over time, due to the effective heat transfer of complete crystal structure. We confirmed that excellent radiant heat properties than powder phosphor was applied to a high power white laser diode.

• Korean Journal of Materials Research
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• v.31 no.5
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• pp.296-300
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• 2021

Al-Cr-Si ternary quench ribbons are fabricated using a single roll method and investigated for their structural and thermal properties. In particular, the sinterability is examined by pulse current sintering to obtain the following results. The Al₇₄Cr₂₀Si₆ composition becomes a quasicrystalline single phase; by reducing the amount of Cr, it becomes a two-phase mixed structure of Al phase and quasicrystalline phase. As a result of sintering of Al₇₄Cr₂₀Si₆, Al₇₇Cr₁₃Si₁₀ and Al₉₀Cr₆Si₄ compositions, the sintering density is increased with the large amount of Al phase; the sintering density is the highest in Al₉₀Cr₆Si₄ composition. In addition, as a result of investigating the effects of sintering temperature and pressurization on the sintered density of Al₉₀Cr₆Si₄, a sintered compact of 99% or more at 513 K and 500 MPa is produced. In particular, since the Al-Cr-Si ternary crystal is more thermally stable than the Al-Cr binary quaternary crystal, it is possible to increase the sintering temperature by about 100 K. Therefore, using an alloy of Al₉₀Cr₆Si₄ composition, a sintered compact having a sintered density of 99 % or more at 613 K and 250 MPa can be manufactured. It is possible to increase the sintering temperature by using the alloy system as a ternary system. As a result, it is possible to produce a sintered body with higher density than that possible using the binary system, and at half the pressure compared with the conventional Al-Cr binary system.

• Journal of the Korean Ceramic Society
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• v.29 no.6
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• pp.463-470
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• 1992

Corundum single crystals were grown in cryolite flux with the composition of Na3AlF6:Al2O3=80:20 wt%. This mixture was melted at 115$0^{\circ}C$, followed by slow cooling at a rate of 2$^{\circ}C$/hr to 96$0^{\circ}C$. And by adding of La2O3 to the flux, the change of crystal forms were observed. Crystal forms of corundum grown in cryolite flux had the habits of hexagonal plate which consist of well developed {0001} face and small {101} face. As La2O3 was added and its content was increased, {223} and {110} faces were developed, and crystal habits of equidimensional forms changed into hexagonal prism form. In a charge of 8 mole% B2O3, Al2O3:La2O3=15:1, transparent corundum single crystals of equent form were grown. As the content of B2O3 was increased, twineed crystals which have twin law of 2-fold parallel to [0001], and composition plane of (110) were grown.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.1694-1695
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• 2007

DC-Motor is needed more and more sophisticated control to follow the highest precision of industrial automation and used in a number of control equipment or industrial fields. It is also useful to control single crystal(Al2O3) growth. It is possible to procure a quality crystal utilizing a DC-Motor, if you mix Hydrogen and Oxygen gas properly and keep proper temperature in accordance with time process. In this paper, we will study about electrical valve positioning system for the gas mixture to improve the quality of single crystal($Al_{2}O_{3}$) growth and we will design about realtime monitoring systems of the automatic gas contol DC- Motor for single crystal($Al_{2}O_{3}$) growth

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.24 no.2
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• pp.54-58
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• 2014

AlN (Aluminum Nitride) crystals were grown by a PVT (Physical Vapor Transport) method and were characterized to phases on the growth temperature. The crystals phase and morphology were analyzed using an optical stereo-microscope and the optimum temperature for the growing was determined. In this report, the characteristics of the AlN crystals grown at various temperatures were reported.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.29 no.3
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• pp.140-142
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• 2019

AlN (Aluminum Nitride) crystal which could be used to substrates for UV LEDs was grown by PVT ((Physical Vapor Transport) method. 3 inch AlN single crystal with a thickenss of 4 mm was grown using Polycrystalline seed for 120 hours. In this report, a result of 3 inch polycrystalline bulk AlN growth behavior using large size crucible and growth condition were reported.