• Journal of the Korean Ceramic Society
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• v.40 no.9
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• pp.916-920
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• 2003

The change of structure and morphology in ( $U_{0.913}$G $d_{0.087}$) $O_2$ during oxidation at 475$^{\circ}C$ and heat treatment at 130$0^{\circ}C$ in air were investigated using XRD, SEM, and EPMA. The ( $U_{0.913}$G $d_{0.087}$) $O_2$ cubic phase converted to ( $U_{0.913}$G $d_{0.087}$)$_3$ $O_{8}$ orthorhombic phase by oxidation at 475$^{\circ}C$ in air. The XRD and EPMA result of the 130$0^{\circ}C$ heat treated powder revealed that ( $U_{0.913}$G $d_{0.087}$)$_3$ $O_{8}$ orthorhombic phase was separated into $U_3$ $O_{8}$ and ( $U_{0.67}$G $d_{0.33}$) $O_{2+}$x/ cubic phase. The weight variations of (U,Gd) $O_2$ with various Gd contents were measured using TGA at the same heat treated condition. The weight variation during the heat treatment of Gd dissolve (U,Gd) $O_2$ in air can be expressed in terms of phase reaction equations related with oxidation and phase separation. Based on these phase reaction, a initial content of Gd dissolved in (U,Gd) $O_2$ can be exactly calculated by measuring the weight change during the heat treatment.

• Journal of the Korean Ceramic Society
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• v.38 no.5
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• pp.474-478
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• 2001

유기 화학 기상 증착법(MOCVD)을 이용하여 반응기체 $O_2$의 양 및 Y와 Mn의 운반기체 비(Y/Mn)를 변화시켜가며 Si(100) 기판 위에서 MFSFET(metal-ferroelectric-semiconductor field effect transistor) 구조의 YMnO$_3$박막을 증착하였다. 반응기체 $O_2$의 양이 150sccm일 때 Y/Mn=2와 3인 경우 단일상의 육방정계 YMnO$_3$박막이 형성되었다. YMnO$_3$박막의 전기적 특성은 사방정계 YMnO$_3$박막에서는 나타나지 않았으나, 육방정계 YMnO$_3$박막의 경우 결정립 크기에 영향을 받아 단일상의 육방정계 YMnO$_3$박막 중 결정립 크기가 150nm~200nm(Y/Mn=2)인 경우에는 잔류분극이 100nC/$ extrm{cm}^2$인 P-E 이력곡선의 특성을 나타내었다.

• Korean Journal of Crystallography
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• v.7 no.1
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• pp.20-29
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• 1996

Sr0.6Ca0.4CuO2 single crystal has been synthesized by flux method and characterized by the single crystal X-ray diffraction. The compound has the orthorhombic system and the space group is Cmcm(63), lattice parameters are a=3.4645Å, b=16.1417Å, c=3.8727Å. In the (Sr1-xCax)CuO2 compound the limit of Ca from substitution for Sr was determined by the change of bond length. For this, X-ray diffraction, scanning electron microscopy (SEM), energy dispersive X-ray fluorescence (EDAX) and electron probe micro-analysis (EPMA) were used. From the change of Cu-O bond length as the Ca substitution, we concluded the limit of Ca incorporation Xca≒0.73.

• The Korean Journal of Rheology
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• v.5 no.2
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• pp.149-160
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• 1993

표면성장법을 이용한 고강력, 고탄성률 섬유의 제조시, 결정화 온도에 따른 섬유 미 세구조와 물리적 성질의 상관 관계를 미세구조적, 열역학적 관점에서 규명하고자 초고분자 량 폴리에틸렌으로 섬유를 제조하고 결정화 온도에 따른 구조와 인장 성질의 변화를 용융 거동을 중심으로 관찰하였다, 일정길이하에서의 섬유의 용융인 제한 용융에서는 고분자 사 슬배좌의 구속으로 인해 사방정계-육방정계 전이가 일어났다 제한 용융 거동으로부터 라멜 라 구조와 펼쳐진 사슬 결정 부분을 분리할 수 있었으며 결정화 온도가 증가할수록 펼쳐진 사슬 결정의 양이 증가하였다. 결정화 온도가 증가할수록 쉬시-케밥구조에서 펼쳐진 사슬 구조로의 변화가 일어났으며 결정내의 결점도 줄어들었다. 결정화 온도가 증가할수록 구조 의 변화로 인해 인장 성질이 향상되었다. 인장 성질은 펼쳐진 사슬 결정의 양에 큰 영향을 받았다. 인장 강도는 펼쳐진 사릉의 양과 사슬내의 결점들에 의해 큰 영향을 받았으며 인장 탄성계수와 절단 신도는 인장 강도보다 펼쳐진 사슬의 양에 더 크게 영향 받았다.

• Proceedings of the Korea Crystallographic Association Conference
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• 2002.11a
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• pp.11-11
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• 2002

K(H/sub 0.34/D/sub 0.66/)₂PO₄는 KH₂PO₄(KDP)의 수소원자를 중수소가 일부 치환한 결정이다. 실험에 사용한 시료는 KDP 원료시약을 중수(D₂O)에서 성장시킨 것으로, 단결정 구조해석을 통해 D와 H의 점유율을 정련하였다. 본 연구에서는 상전이에 따른 결정구조의 변화를 연구하기 위하여 한국원자력연구소의 연구용 원자로인 하나로에 설치된 고분해능 분말회절장치(HRPD)로 상온에서부터 10K 까지 온도를 변화시켜가며 회절패턴을 측정하였다. 그 결과 190-l95K 사이에서 상전이가 일어났으며, 이것은 DSC(Differential Scanning Calorimetry) 측정결과와 상온에서 단결정 분석결과 D의 점유도로 계산한 상전이 온도와도 잘 일치한다. 10K와 298K에서 측정한 회절패턴에 대해 프로그램 FullProf를 사용하여 각각 리트벨트 구조정련을 수행한 결과, 상온에서는 정방정계이며 공간군은 I-42d 이고 저온에서는 사방정계인 Fdd2로 변한다. 온도변화에 따른 핵밀도 분포를 측정한 결과 상온에서 D/H는 2회 대칭축을 중심으로 50％ 점유도의 두 가지 가능한 위치를 갖는 무질서(disorder) 상태로 존재하나 온도가 내려갈수록 한 쪽으로 치우쳐 상전이 온도 아래에서는 하나의 산소와 결합하여 질서(order) 상태를 보이며 다른 하나와는 수소결합을 이룬다.

• Korean Journal of Crystallography
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• v.9 no.2
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• pp.138-142
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• 1998

Lithium triborate, LiB3O5(Mr=119.37), 단결정을 상단 종자정 융액법으로 성장시켰으며, 결정구조를 X-선 회절법으로 연구하였다. 결정계는 사방정계이며 공간군은 Pna21(No. 33)이다. 단위포의 상수는 a=8.432(1) , b=7.364(1) , c=5.110(1) , α=β=γ=90.00o, V=317.3(6) 3, V=4, Dx=2.50 gcm-3, MoKα1, λ=0.71069 , μ=2.3/cm, F(000)=232, T=293 K 이었다. 최종 구조의 오차인자는 520개 회절 점에서 각각 R=0.0222과 wR=0.0582이었다.

• Electrical & Electronic Materials
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• v.9 no.4
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• pp.379-384
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• 1996

The microwave dielectric properties of (I-x)CaTiO$_{3}$-xLaAIO$_{3}$ were investigated. The solid solution of (1-x)CaTiO$_{3}$-xLaAIO$_{3}$ had the perovskite structure in the range of all compositions. The crystal system of (1-x)CaTiO$_{3}$-xLaAIO$_{3}$ was transformed to orthorhombic(x.leq.0.4), psudo-cubic(x=0.5), and rhombohedral (x.geq.0.7) in turn, as the amount of LaAIO$_{3}$ increased. The dielectric constant and temperature coefficient of resonant frequency of solid solution were decreased with the content of LaAIO$_{3}$, whereas, the value of Q . f$_{o}$ was increased. The microwave dielectric material having Q . f$_{o}$ = 32, 500, .epsilon.$_{r}$ = 42, and .tau.$_{f}$ = 5 ppm/.deg. C was obtained from the 0.35CaTiO$_{3}$-0.65LaAIO$_{3}$ composition sintered at 1600.deg. C for 4hrs.hrs.hrs.

• Journal of the Mineralogical Society of Korea
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• v.1 no.2
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• pp.104-116
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• 1988

Berthierine and Nontronite are firstly identified in the Sangdong tungsten ore deposits. Quantitative and qualitative analyses by EPMA and the studies using X-ray diffraction, transmission electron microscopy, and infrared absorption spectroscopy were done to characterize berthierine and nontronite. The data from berthierine are in good agreement with those from other localities. The structural data of the Sangdong berthierine are consistent with the orthorhombic, pseudo-hexagonal form which is more common in samples with high $SiO_2$ and low $Al_2O_3$ content. Geologic features suggest that the Sangdong berthierine is diagenetic in origin. However, nontronite might be a product of hydrothermal alteration after the tungsten mineralization.

• Journal of the Korean Chemical Society
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• v.39 no.7
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• pp.508-512
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• 1995

A series of samples in the $Eu_{1-x}Sr_xCoO_{3-y}$ system has been prepared by heating the proper amount of reactant mixture to 1150$^{\circ}C$ under an ambient atmosphere, and the solid solutions are identified by X-ray powder diffraction analysis. The crystal system of samples for the compositions of x=0.00 and 0.25 are found to be orthorhombic whose local symmetry is similiar to the distorted octahedra with orthoferrite type one, whereas those of x=0.50 and 0.75 to be the cubic system, and that of x=1.00 to the orthorhombic similiar to be the brownmillerite type. The amount of $Co^{4+}$ ion (${\tau}$ value) is maximized at the composition of x=0.50, and the oxygen vacancies increase with the x value. The nonstoichiometric chemical formula of each compound could be determined from the mole ratio of $Co^{4+}$ ion and oxygen vacancies. The $Co^{3+}$ ion located in octahedral site has spin transition from low spin to high spin states with increasing temperature. Therefore, the effective magnetic moment of each samples obtained from the magnetic measurement is increased with the increasing temperature. The $EuCoO_{3.00}$ has strong antiferromagnetic interaction between the neighboring $Co^{3+}$ ions through the intermediate oxygen ions. With the increasing ${\tau}$ value, the absolute {\theta}_p$ value is decreased by the ferromagnetic interaction of $Co^{3+}-O^2-Co^{4+}$ and thus the {\theta}_p$ has positive value at x=0.50.

• Journal of the Mineralogical Society of Korea
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• v.16 no.2
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• pp.161-169
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• 2003

A phase transformation study on a synthetic amorphous diopside, $(Ca,Mg)SiO_3$has been carried out up to ∼30 GPa, and ∼$1000^{\circ}C$ using a diamond anvil cell and YAG laser heating system, respectively. A starting amorphous material shows a direct transition to cubic $(Ca,Mg)SiO_3$perovskite at high pressure, which contradicts to the crystalline diopside phase transformation sequence disproportionating into mixtures of the orthorhombic$ MgSiO_3$perovskite and the cubic $CaSiO_3$perovskite phases. This discrepancy might be due to the different starting materials as well as the temperature variations at each specific experiment performed. The present phase transfor mation sequence would modify the mineralogical assemblage in the Earth transition region and the lower mantle depending upon the pressure, temperature and the oxygen partial pressure.