• Solar Energy
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• v.12 no.3
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• pp.107-115
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• 1992

An experiment was performed to study solidification of binary mixture with double-diffusive convection in the liquid. A rectangular enclosure was filled with ammonium chloridewater solution. The phase change and convection process were studied through shadowgraph. Becasuse of the double-diffusive convection, the temperature field and concentration filed were stratified very rapidly. Correlation between solidified mass fraction and the dimensionless numbers was found; solidified mass concentration can be expressed as a linear function of $(Ste{\cdot}Ra^{1/4})^{2-Ste}{\cdot}Fo^{1/2}$.

• Korean Journal of Crystallography
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• v.3 no.1
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• pp.37-43
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• 1992

KTiOP04 is a nonlinear optical crystal which is most widely used for frequency doubling of the radiation of Nd : YAG laser. In the experiment, sin ale crystals of KTiOP04 were grown by TSSG technique using 3K2W04·P2O5 flux. Low temperature gradient furnace suitable for KTP single crystal growth was used. Seed crystal was placed at the surface of the solution for the purpose of better observation of the growing crystals and the possibility of diameter control. Solution included 66.7mol% KTiOP04 for all experiments and its saturation temperature was 1020℃. The conditions of single crystal growth were as follows: cooling rate 0.2℃/h, crystal rotation rate 50rpm, c -axis seed. Using these conditions, single crystals up to 23 ×25×25mm3 have been groan from about 100cc solution. We have also observed a change in the crystal growth habit which resulted in the formation of large (201) faces and small (100) faces. And some crystals have (101) faces.

• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.6
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• pp.1321-1329
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• 1989

본 논문에서는 성층화된 용액ㅇ네 수평방향으로 온도구배가 가해지는 경우에 있어서 두 부력인자의 상대적 크기에 따라 나타나는 유동형태와 그에 따른 온도, 농도 분포 및 열전달특성을 수치적으로 연구하고자 한다.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.3 no.1
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• pp.12-17
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• 1993

Growth runs of KTP single crystals were carried out by the hydrothermal method. KTP powders used for the crystal growth were prepared as a single phase by the solid state reaction of a stoichiometric mixture of $KH_2PO_4 and TiO_2$ at TEX>$800^{\circ}C$ and subsequently by the hydrothermal treatment at $250^{\circ}C$ 4m KF solution. The most effective solvents for the crystal growth of KTP were KF and K $K_2HPO_4$ solutions. Solubilities of KTP in these solutions were positive over the range $350~450^{\circ}C$.Seed crystals of good quality could be obtained by the horizontal temperature gradient method at temperatures over the range 380~430^{\circ}C$ in these solutions. The hydrothermal conditions for the high growth rates of seed crystals are as follows: growth method; vertical temperature gradient method, solvent; 4m KF or $K_2HPO_4$ solution, temperature region; $400~450^{\circ}C$, pressure region; $1000~1500kg/cm^2$, where solubility of KTP was large enough to proceed the growth. Under such conditions, seed crystals of KTP are grown at a rate of approximately 0.06-0.08mm/day in the direction of the c-axis. Morphologies of grown crystals tended to be bounded by (100), (011) and (201) faces.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 1996.06b
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• pp.239-257
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• 1996

$\beta$-BaB2O4는 고출력 가시광선 및 적외선을 발진시키는데 유용한, 비선형 특성을 가진 물질이다. $\alpha$-$\beta$ 상전이 온도가 녹는점보다 18$0^{\circ}C$ 낮기 때문에 보통 flux법으로 단결정을 성장시킨다. 수년전 Itoh등은 $\beta$-BaB2O4단결정을 congruent조성의 용액으로부터 Czochralski법으로 metastable한 상태에서 직접 성장시켰다. 그렇지만 그 공정은 잘 이해되지 않고 있으며 재현하기가 매우 어렵다. 저자들은 $\beta$-BaB2O4단결정을 용액표면온도도 1034$^{\circ}$-1085$^{\circ}C$, pulling rate 3mm/h, 10-30 rpm의 범위에서 성장시켰으며 융액표면의 온도구배는 $\beta$-상으로 성장시키는데 매우 중요한 인자로 여겨진다. Seed로는 직경 1-2mm의 c축방향 $\beta$-BaB2O4단결정 봉이 상용되어 성장방향을 조절하고 열응력을 최소화시켰다. 성장된 $\beta$-상의 단결정들은 6-fold모양을 하며 표면에 작은 비늘같은 것들이 붙어있고 중심부에 core가 있는 것을 알았다. Flux법으로 성장시킨 $\beta$-BaB2O4단결정을 사용한 seeds는 단결정 성장 및 냉각 중에 cracks이 자주 발생하였으며, boule의 cracks은 afterheater를 사용할 경우 다소 줄일 수 있었다. 성장된 단결정의 광학특성이 측정되었다.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.4 no.1
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• pp.100-104
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• 1994

KTP seed crystals were grown by the hydrothermal method and the properties of grown crystals were investigated by means of infrared spectrophotometer. The hydrothermal conditions for high growth rates of seed crystals are as follows: temperature ranges, between , $430 and 450^{\circ}C $ ; hydrothermal solvent, 4m KF solution ; temperatures difference, $30<{\triangle}T<65^{\circ}C$ ; filling %, 65% ; growth method, vertical temperature gradient method. Under these conditions, morphologies of the grown KTP single crystals tended to be bounded by (100), (011) and (201) faces and hydroxyl groups were observed in the grown crystals.

• Electrical & Electronic Materials
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• v.7 no.4
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• pp.312-316
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• 1994

In this study, ln$_{1-x}$ Ga$_{x}$P alloy crystal which has different compositions were grown by the temperature gradient solution(TGS) method, and the properties of deep levels were measured in the temperature range of 9OK-450K. We find the four deep levels of E$_{1}$, E$_{2}$(248meV), E$_{3}$(386meV) and E$_{4}$(618meV) in GaP, which has composition of Ga in In$_{1-x}$ Ga$_{x}$P is one, and the trap densities of E$_{3}$ and E4 levels were 7.5*10$^{14}$ cm$^{-3}$ and 9*10$^{14}$ cm$^{-3}$ , respectively. A broad deep level spectra was revealed in In$_{1-x}$ Ga$_{x}$P whose composition of Ga, x, were 0.56 and 0.83, and the activation energy and trap densities were about 430meV and 6*10$^{14}$ cm$^{-3}$ , respectively.ectively.

• Korean Journal of Crystallography
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• v.7 no.1
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• pp.30-35
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• 1996

Calcite(CaCO3) single crystals were grown hydrothermally and transmittance of as grown crystals was measured. Instead of platinium, teflon was lined onto the wall of autoclave to prevent the corrosion of autoclave wall by acidic NH4Cl solution. Spontaneous nucleation and growth of calcite crystal on teflon was reduced considerably by addition of NaCl and /or CH3COOH and applying low temperature gradient. When the temperature gradient exceeded to a few degrees from the critical temperature gradient(6-7℃), spontaneous nucleation and growth was rapidly increased in any hydrothermal solutions. Precise temperature control is thought to be the most important factor for the growth of calcite single crystal by hydrothermal technique. As grown calcite single crytal showed high transmittance compared to natural one by UV-visible analysis.

• Korean Journal of Crystallography
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• v.8 no.1
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• pp.15-19
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• 1997

Single crystals of Co-doped quartz (blue quartz) were grown hydrothermally from the $Na_2CO_3$ solution. The size of as-grown crystal was $100{\times}50{\times}35mm^3$ and the growth rate was 0.55 mm/day under the growth condition of $5wt.\%\;Na_2CO_3$ mineralizer, growth temperature of $343^{\circ}C$ and temperature gradient of $22^{\circ}C$. Visible spectrum showed a typical absorption feature of the synthetic blue quartz near 545, 570 and 643 nm. The concentration of color of the as-grown blue quartz related not to the concentration of cobalt in raw material but to the growth temperature.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.27 no.3
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• pp.130-134
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• 2017

In this study, numerical simulation was performed to focus on optimized process condition for obtaining a long-term growth and high quality SiC crystal. It could be optimized by considering the change of fluid and a carbon flow in the Si melt added with 40 % Cr. The Crystal Growth Simulator ($CGSim^{TM}$, STR Group Ltd.) was used as a numerical simulation. It was confirmed that many parameters such as temperature, rotation speed of seed crystal and crucible, and seed position during the crystal growth step had a strong influence on the speed and direction of solution flow for uniform temperature gradient and stable crystal growth. The optimized process condition for the solution growth of SiC crystal was successfully exhibited by adjusting various process parameters in the numerical simulation, which would be helpful for real crystal growth.