• 한국결정성장학회지
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• 제3권1호
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• pp.85-92
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• 1993

커다란 olivine 단결정을 image furnace(floating zone furnace)를 사용하여 산소분압의 조절하에서 성장시켰다. 결정은 투명하였으며 길이가 65mm, 직경이 8mm였다. 산소분압이 감소할 때 결정내 제2상이 증가하여 결정을 엷은 갈색에서 짙은 갈색으로 변화시켰다. 이 제2상은 EPMA결과 Mg가 기저를 이룬 것에 Si와 Fe가 solid solution을 형성한 것이었다.

• 한국결정성장학회지
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• 제2권1호
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• pp.20-29
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• 1992

전영역에 결쳐서 고용영역이 존재하는 $BaTiO_3-NaNbO_3$계에서, congruent melting composition인 $30BaTiO_3{cdot}70NaNbO_3$조성의 고용체 단결정을 Czochralski법에 의하여 육성하였다. 직경 15-50mm, 길이 20-30mm인 단결정이 결정인상속도 2.0mm/h, 결정회전수 5.0-1-rpm에서 육성되었다. 그러나 결정 육성중 육성되는 결정의 열전도도가 낮기 때문에, 발생하는 잠열(latent heat)의 방출이 충분치 않아 고-액계면이 평탄하게 유지되지 않았고 그결과로 육성된 결정중에는 corestructures가 관찰되었다. 육성된 결정에서 core 부분을 제외한 다른 부분은 inclusion등이 없는, 광학적으로 균질한 단결정이었고 가시광 영역에서 양호한 광투과율을 보였다.

• 한국결정성장학회지
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• 제1권2호
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• pp.1-14
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• 1991

비균질 용융을(incongruent melting behavior)보이는 단결정제조에 있어 화학성분을 일정성분비로 유지하는 것은 매우 어렵다. $LiNbO_3$는 이러한 성질을 보이는 대표적인 예인데 넓은 고용(固溶)영역에서 일정성분비를 유지하기 힘들다 . 정밀전기/ 광학장치에 있어 이런 변수는 치명적이라 할 수 있다. 결정의 조성과 질을 결정하는 방법으로 굴절율(n)을 측정하는 광학적 방법이 수행되어 왔다. 이 방법으로 성장결정의 광학적 균질성과 화학조성을 알아낼 수 있다. 여기서는 그런 특성분석에 사용 되는 기술을 설명하고 그 결과들을 제시해 보았다

• 한국환경과학회지
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• 제15권2호
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• pp.177-183
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• 2006

The hydrolytic kinetics of biodegradable poly(l-lactide) (PLLA) have been studied by using two model systems, solution-grown single crystal (SC) and Langmuir monolayer techniques, for elucidating the mechanism for both alkaline and enzymatic degradations. The present study investigated the parameters such as degradation medium and time. The Langmuir mono layers of PLLA showed faster rates of hydrolysis when they were exposed to a basic subphase rather than they did when exposed to neutral subphase. Both degradation mediums had moderate concentrations to show a maximized activity, depending on their sizes. An alkaline degradation of SCs of PLLA showed the decrease of molecular weight of the remained crystals due to the erosion of chain-folding surface. However, the enzymatic degradation of SCs of PLLA occurred in the crystal edges thus the molecular weight of remained crystals was not changed. This behavior might be attributed to the size of enzymes which is much larger than that of alkaline ions; that is, the enzymes need larger contact area with monolayers to be activated.

• 한국재료학회지
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• 제22권8호
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• pp.397-402
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• 2012

Morphological control on hydroxyapatite crystals has attractive prospects in research to clarify the effects of crystal planes on biological performance. Hydrothermal processing is known as a typical type of processing for fabricating well-grown crystals with unique morphology. The purpose of the present study is to examine the feasibility of well-crystallized crystals with oriented structures through hydrothermal treatment of calcite. A single crystal of calcite was applied to hydrothermal treatment in a phosphate solution at $160^{\circ}C$. Rod-shaped hydroxyapatite crystals with micrometer-size were formed on the {100} face of calcite after treatment, while nanometer-sized hydroxyapatite crystals were formed on the (111). The hydroxyapatite crystals formed on each plane were not morphologically changed with increasing treatment periods. An oriented structure of rod-shaped hydroxyapatite was constructed after hydrothermal treatment of {100} planes on the calcite single, while such orientation was not observed on the (111) plane after the treatment. The layer of hydroxyapatite formed on the {100} plane was thicker than that of the (111) plane. The {100} plane of calcite shows a higher reactivity than that of the (111) plane, which results in rapid crystal growth of hydroxyapatite. The difference in the morphology of the formed hydroxyapatite was governed by the reactivity of each crystal plane exposed to the surrounding solution.

• 한국결정성장학회:학술대회논문집
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• 한국결정성장학회 1997년도 Proceedings of the 12th KACG Technical Meeting and the 4th Korea-Japan EMGS (Electronic Materials Growth Symposium)
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• pp.149-155
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• 1997

We have successfully grown colorless and transparent Rb-doped potassium niobate (KRN) single crystals using the top seeded solution growth(TSSG) technique. In our crystal growth experiments, the Rb doping concentrations within the melt range from 2-15 mol% relative to that of Nb$_2$O5. Atomic absorption measurements indicate that the Rb content in the KRN solid solution is rather low; the Rb segregation coefficient is found to be on the order of 0.05. It is believed that this is due to the relatively much larger Rb+ ionic radius compared to that of K+, rendering it more difficult for Rb to replace K in the KNbO$_3$(KN) host lattice. Preliminary single-pass second harmonic generation (SHG) experimental results indicate that there exists marginal improvement in the phase-matching temperature tolerance of KRN compared to that of pure Kn single crystals.

• 한국결정성장학회:학술대회논문집
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• 한국결정성장학회 1998년도 PROCEEDINGS OF THE 14TH KACG TECHNICAL MEETING AND THE 5TH KOREA-JAPAN EMGS (ELECTRONIC MATERIALS GROWTH SYMPOSIUM)
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• pp.7-10
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• 1998

L-Histidine tetrafluoroborate single crystals have been grown from the aqueous solution. The profitable pH value to grow large crystals, the relative flow rate to get clear crystals, crystals habit and the orientation of the obtained crystal have been clarified. We have also demonstrated that the LHBF crystal has very high damage threshold which is potentially good for generation of the phase conjugated waves.

• 한국결정성장학회:학술대회논문집
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• 한국결정성장학회 1999년도 PROCEEDINGS OF 99 INTERNATIONAL CONFERENCE OF THE KACG AND 6TH KOREA·JAPAN EMG SYMPOSIUM (ELECTRONIC MATERIALS GROWTH SYMPOSIUM), HANYANG UNIVERSITY, SEOUL, 06월 09일 JUNE 1999
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• pp.227-250
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• 1999

The reproducibility of successive growth of Bi12TiO20(BTO) single crystals using a top-seeded solution growth (TSSG) pulling method was evaluated by measuring the lattice constants and their standard deviations. A substantial phase diagram in the region close to the stoichiometric BTO was established experimentally for this purpose, and the existence of a retrograde solid solution close to a BTO was clarified. It was emphasize that a starting solution, with a 10.0~10.1 mol% TiO2 concentration, results in large single crystals with a highly homogeneous lattice constant of within $\pm$1x10-4$\AA$, when the solidified fraction of the grown crystal is less than about 45%. A wavelength dispersion of refractive index was measured for the first time, an it was verified that the refractive index of BTO is larger than that of BSO(Bi12TiO20), allowing the voltage sensitivity of EOS higher than the case with BSO as a probe head.

• 한국결정성장학회:학술대회논문집
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• 한국결정성장학회 1999년도 PROCEEDINGS OF 99 INTERNATIONAL CONFERENCE OF THE KACG AND 6TH KOREA·JAPAN EMG SYMPOSIUM (ELECTRONIC MATERIALS GROWTH SYMPOSIUM), HANYANG UNIVERSITY, SEOUL, 06월 09일 JUNE 1999
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• pp.167-185
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• 1999

In the present paper, KLN crystals have been grown along <001>, <100> and <110> directions by the top seeded solution growth (TSSG) method from Li-richer melts with different compositions. The morphologies of KLN crystals grown along different directions have been studied, and the well-developed facets have been unambiguously indexed using X-ray goniometer and stereographic projection analysis. The growth mechanism and defects such as cracks and inclusions were discussed on the basis of observations of facets on the crystal-melt interfaces. The crystal compositions were determined by chemical analysis method. The structure and lattice constants of KLN crystals were determined and calculated on the basis of XRD data by using TREOR90 and PIRUM programs. The Curie temperature and optical absorption were determined by dielectric constant peak and spectrum measurements, respectively. The blue SHG characteristics of a KLN sample were also investigated using a pulsed dye laser. PACS: 42.70.M;81.10;81.10A;42.65.K.

• 한국결정성장학회지
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• 제4권3호
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• pp.223-229
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• 1994

$KTP(KTiOPO_4)$ 단결정을 KOH 용액 중에서 수열적으로 육성하였다. 그리고 육성결 정에 대하여 물성 및 Raman spectra를 조사하였다. KTP 단결정의 육서에 있어 KOH와 KF용 액이 효과적인 수열용매이었다. 본 연구에서는 $500^{\circ}C$의 9몰 KOH 용액 중에서 수열육성시킨 KTP 단결정을 갖고 물성조사를 하였으며 그 결과는 다음과 같다. 즉, 격자정수: a = 1.281 nm, c=1.058nm, 밀도: $2.94 g/cm^3$, Vickers 경도: $562kg/cm^2$, 굴절율: $n_e=1.740$, $n_e= 1.747.$이었다. 그리고 수열 육성 KTP 단결정의 Raman spectra를 상온, 상압하에서 조사한 결과 $A_1$ mode는 고온 용액법의 KTP 단결정과 동일 하였으나 $B_2$ mode의 거동은 약간 다르게 관측되었다.