• Korean Journal of Crystallography
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• v.7 no.2
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• pp.196-200
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• 1996

The transformation processes from unit cell data, Miller indices and atomic coordinates of non-standard space groups to the ones of the standard space groups in monoclinic system and the calculation processes of their standard deviations have been shown and computerized. The computer programs can be applied to all the seven crystal systems.

• Proceedings of the Korean Fiber Society Conference
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• 2001.10a
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• pp.275-278
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• 2001

나일론 11[poly(undecanolactam)]은 적어도 5개의 결정형태를 가지며 삼사정계의 $\alpha$형, 단사정계의 $\beta$형 그리고 3개의 육방정계 또는 가육방정계의 형태(${\gamma}$,$\delta$,$\delta$')를 갖는다고 알려져 있다. $\alpha$형은 95$^{\circ}C$ 이하에서 안정하고 $\delta$형은 95$^{\circ}C$ 이상에서 안정하다. 용융상태 또는 5형에서 급냉하면 준안정 상태의 $\delta$'형을 형성한다. $\alpha$형을 trifluoroacetic acid로 처리하면 안정할 ${\gamma}$형이 얻어진다[1-2]. (중략)

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.92.2-92.2
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• 2010

Selenium 물질은 지구상에 많은 양이 존재하고, 가격이 저렴하다. 그 성질은 분광감도가 시감도에 잘 일치하고, 광학적 특성이 뛰어나서 태양전지로 연구도 활발히 진행 중이다. 본 연구에서는 Se박막을 열저항증착방법을 이용하여 증착시, 기판온도를 변화를 시켜 그 구조적특성의 변화를 관찰하였다. $50^{\circ}C$에서 변화를 시작하여 $70^{\circ}C$, $100^{\circ}C$의 변화에서 각각 단사정계, 육방정계 결정구조가 나타났다. XRD 분석결과 $100^{\circ}C$에서 증착한 sample의 회절강도가 $70^{\circ}C$에서 증착한 sample보다 작은회절강도를 나타내었다. 추후 열처리공정등을 통하여 보완하면, CISe 박막 화합물 태양전지 연구에 큰 효과를 나타낼 수 있을 것으로 예상된다.

• Electrical & Electronic Materials
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• v.9 no.5
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• pp.445-449
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• 1996

Structural and optical characteristics in Se thin film fabricated by EBE method had been studied. Se thin film was deposited with noncrystalline until substrate temperature of >$100^{\circ}C$ Color of its surface had red genealogy, and its optical energy band gap was about 2.45 eV. But Se film was grown with monoclinic at substrate temperature of over >$150^{\circ}C$ Also, color of its surface had gray genealogy, and its optical energy band gap was about 2.31 eV. Finally, after heat-treatment at >$150^{\circ}C$ for 15 min with substrate temperature of >$100^{\circ}C$ noncrystalline Se was proved to be hexagonal, and color of its surface had dark gray genealogy, and its optical energy band gap was about 2.06 eV. From the results, it was known that Se thin film for photoelectric device with the lowest optical energy band gap was accepted from hexagonal structure.

• Korean Journal of Crystallography
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• v.10 no.1
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• pp.45-50
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• 1999

Ar 기류하에서 trans-[FeH(NCCH2CH2CH2Cl)(dppe)2][BF4], 1과 KCN이 반응하여 trans-[FeH(CN)(dppe)2], 2가 생성되었다. 이 화합물의 구조가 NMR, IR, 원소분석, 그리고 X-ray 회절법으로 규명되었다. 착물 2의 결정학 자료: 단사정계 공간군 p21/c, a=13.580(1) b=20.178(2) , c=17.592(3) , β=92.22(1)o, Z=4,(wR2)=0.0659(0.1692).

• Journal of the Korean Chemical Society
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• v.35 no.4
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• pp.324-328
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• 1991

The Li$_2SO_4$ system containing various mol${\%}$ of CaSO$_4$ were synthesized. The structure and the electrical conduction of these system were studied at the temperature from 20 to 700$^{\circ}C$. In the region of CaSO$_4$ mol ratio higher than 0.05, it could be confirmed that Li$_2SO_4-CaSO_4$ system does not form solid solution. Due to the substituted Ca$^{2+}$, the transition temperature (monoclinic to cubic) is shifted to the low temperature. The ionic conduction of monoclinic Li$_2SO_4-CaSO_4$ increased with increasing lithium vacancy which was produced by substituted Ca$^{2+}$, but that fcc Li$_2SO_4-CaSO_4$ was not influenced by the substituted Ca$^{2+}$ ion.

• Journal of the Korean Chemical Society
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• v.39 no.6
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• pp.446-452
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• 1995

Lithium intercalates, $Li_xFeMoO_4Cl$ ($1{\leq}X{\leq}2$) prepared by electrochemical lithiation of $FeMoO_4Cl$ crystallizes in monoclinic structure for all x values as revealed by x-ray diffraction and galvanostatic discharge experiments. According to the x-ray photoelectron spectroscopic study, Fe(III) is at first reduced to Fe(II) upon lithium intercalation with the x domain of $0{\leq}X{\leq}1$, where the crystal symmetry is changed from tetragonal to monoclinic. On the other hand, Mo(VI) is reduced to lower valent state upon further lithium intercalation ($1{\leq}X{\leq}2$), where no crystal symmetry transformation and reduction of Fe(II) to lower valent state are observed. The Mo 3d spectrum for $Li_2FeMoO_4Cl$ appears as a complex shape, but can be deconvoluted into the three sets of the doublet on the basis of Gaussian function, those which correspond to Mo(VI), Mo(V) and Mo(IV) states, respectively. The mixed valent states of molybdenum after further lithiation may be due to a competitive reaction between the formation of Mo(V) and its disproportionation to Mo(IV) and Mo(VI).

• Korean Chemical Engineering Research
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• v.53 no.5
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• pp.620-626
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• 2015

$Ho^{3+}$ doped $SrAl_2O_4$ upconversion phosphor powders were synthesized by spray pyrolysis, and the crystallographic properties and luminescence characteristics were examined by varying activator concentrations and heattreatment temperatures. The effect of organic additives on the crystal structure and luminescent properties was also investigated. $SrAl_2O_4:Ho^{3+}$ powders showed intensive green emission due to the $^5F_4/^5S_2{\rightarrow}^5I_8$ transition of $Ho^{3+}$. The optimal $Ho^{3+}$ concentration in order to achieve the highest luminescence was 0.1%. Over this concentration, emission intensities were largely diminished via a concentration quenching due to dipole-dipole interaction between activator ions. According to the dependence of emission intensity on the pumping power of a laser diode, it was clear that the upconversion of $SrAl_2O_4:Ho^{3+}$ occurred via the ground state absorption-excited state absorption processes involving two near-IR photons. Synthesized powders were monoclinic as a major phase, having some hexagonal phase. The increase of heat-treatment temperatures from $1000^{\circ}C$ to $1350^{\circ}C$ led to crystallinity enhancement of monoclinic phase, reducing hexagonal phase. The hexagonal phase, however, did not disappear even at $1350^{\circ}C$. When both citric acid (CA) and ethylene glycol (EG) were added to the spray solution, the resulting powders had pure monoclinic phase without forming hexagonal phase, and led to largely enhancement of crystallinity. Also, N,N-Dimethylformamide (DMF) addition to the spray solution containing both CA and EG made it possible to effectively reduce the surface area of $SrAl_2O_4:Ho^{3+}$ powders. Consequently, the $SrAl_2O_4:Ho^{3+}$ powders prepared by using the spray solution containing CA/EG/DMF mixture as the organic additives showed about 168% improved luminescence compared to the phosphor prepared without organic additives. It was concluded that both the increased crystallinity of high-purity monoclinic phase and the decrease of surface area were attributed to the large enhancement of upconversion luminescence.

• Journal of Sensor Science and Technology
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• v.2 no.1
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• pp.87-94
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• 1993

CdS and Se thin films were deposited on slide glass by EBE method respectively and surface morphology, crystal structure, electrical and optical properties were investigated by substrate temperature and annealing. The deposited CdS film was well fabricated with cubic structure at substrate temperature of $150^{\circ}C$. Se film was deposited with noncrystal structure until substrate temperature of $100^{\circ}C$, but Se film was grown with monoclinic structure at substrate temperature of $150^{\circ}C$. And so, after annealing at $150^{\circ}C$ for 15min, noncrystalline Se was proved to be hexagonal structure. Finally, the maximum output of Se/CdS heterojunction at 5000 lux was 4 $mW/cm^{2}$ and maximum spectral sensitivity was represented at 585nm.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.221-221
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• 2016

최근에 희토류 이온이 도핑된 텅스텐산(tungstates) 형광체에 대한 연구가 재조명되고 있다. 텅스텐산 형광체는 우수한 광학적 특성과 높은 화학적 안정성을 나타내기 때문에 X-선 증강 스크린(X-ray intensifying screens), 광고판용 형광 램프, 발광 다이오드, 레이저, 섬광체(scintillator), 전계방출 디스플레이 영역에 그 응용성을 넓히고 있다. 본 연구는 모체 결정 MgWO4에 희토류 이온인 Tb3+와 융제(flux)의 몰 비를 변화 시켜 고상반응법을 사용하여 합성을 하였다. 합성한 형광체를 여기 파장 281 nm로 제어하였을 시, 545 nm의 녹색 발광 스펙트럼을 관찰 하였다. Tb3+이온이 0.10 mol일 때, 가장 발광 세기가 컸으며, 몰비가 증가 할수록 발광의 세기는 점차 커지다가 0.12 mol에서 작아졌다. 주 발광 신호 이외에도 489 nm, 586 nm, 621 nm에서 상대적으로 작은 발광 스펙트럼을 보였다. XRD를 통해 분석한 결정구조는 단사정계임을 알 수 있었으며 주 피크는 $23.9^{\circ}$에서 발생 하였고 이는 (110)면에서 발생한 회절 신호이다.