• Title/Summary/Keyword: lattice constant

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The Magnetism and Electronic Structures of Ru Monolayer with Square Lattice (사각형구조를 갖는 Ru 단층의 자성과 전자구조)

  • 조이현;김인기;이재일;장영록;박인호;최성을;권명회
    • Journal of the Korean Magnetics Society
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    • v.9 no.3
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    • pp.127-130
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    • 1999
  • The magnetism and electronic structure of Ru monolayer with square lattice is investigated using the FLAPW band method. The dependence of total energies on the lattice constant was calculated for three magnetic states, i.e.,para-,ferro-, and antiferromagnetic ones. It was found that there is no energy difference between para-and antiferromagnetic states for all the lattice constant. The possibility of antiferromagnetism in square Ru monolayer is thus excluded. The ferromagnetic state is most stable for the lattice constants greater than 7.30 a.u. The energy minimum is found at the lattice constant of 6.53 a.u. Where it is paramagenetic. It is calculated that the magenetic moment is 2.49 ${\MU}_B$ at 7.72 a.u., which is close to the lattice constant of Ag. The magnetic moment is almost saturated to be ${\MU}_B$ at the lattice constant of 7.86 a.u.

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Electrical Properties of SrRuO3 Thin Films with Varying c-axis Lattice Constant

  • Chang, Young-J.;Kim, Jin-I;Jung, C.U.
    • Journal of Magnetics
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    • v.13 no.2
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    • pp.61-64
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    • 2008
  • We studied the effect of the variation of the lattice constant on the electrical properties of $SrRuO_3$ thin films. In order to obtain films with different volumes, we varied the substrate temperature and oxygen pressure during the growth of the films on $SrTiO_3$ (001) substrates. The films were grown using a pulsed laser deposition method. The X-ray diffraction patterns of the grown films at low temperature and low oxygen pressure indicated the elongation of the c-axis lattice constant compared to that of the films grown at a higher temperature and higher oxygen pressure. The in-plane strain states are maintained for all of the films, implying the expansion of the unit-cell volume by the oxygen vacancies. The variation of the electrical resistance reflects the temperature dependence of the resistivity of the metal, with a ferromagnetic transition temperature inferred form the cusp of the curve being observed in the range from 110 K to 150 K. As the c-axis lattice constant decreases, the transition temperature linearly increases.

Preparation and Luminescent Properties of SrTiO3 : Al, Pr Red Phosphors for the FED (FED용 Al 및 Pr 첨가 SrTiO3 적색 형광체의 제조와 발광특성)

  • Park, Chang-sub;Lee, Jeng-Un;Yu, Il
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.18 no.9
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    • pp.846-850
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    • 2005
  • [ $SrTiO_3$ ]:Al, Pr red phosphors for FED were synthesized by solid state reaction method. The dependence of their luminescent properties on Sr and Al concentration was investigated. The $SrTiO_3$: Al, Pr phosphors showed the characteristic X-ray diffraction patterns of the perovskite structure. Photoluminescence intensity and lattice constant in $SrTiO_3$: Al, Pr phosphors changed in quite a similar manner with Sr concentration. Photoluminescence intensity increased with increasing lattice constant, and the decrease of photoluminescence intensity and lattice constant occurred in the vicinity of 1 mol Sr concentration.

Accuracy Improvement of Lattice Parameters Measured from Electron Diffraction Data (전자회절을 이용한 격자상수의 측정 정확도 향상)

  • Lee, Sang-Gil;Song, Kyung;Kim, Jin-Gyu
    • Applied Microscopy
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    • v.41 no.1
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    • pp.75-79
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    • 2011
  • For quantitative analysis of nano-crystal structure, we reported the accuracy improvement method of lattice parameters measured from electron diffraction. For calculation of Au lattice parameters used as a standard crystal structure, it was considered two different acquisition methods (detector and enegy-filter) and three different calculation methods (conventional, least-square and regression fit). As a result, the measurement reliability could be enhanced by using CCD camera which gives higher performance, while energy-filtering did not affect the improvement the camera constant accuracy. Also, the accuracy of lattice parameters could be improved up to $10^{-4}$ order by regression fitting with correction formula. Finally, it is expected that the combination of regression fitting and intensity extraction from energy-filtered precession electron diffraction gives a solution of quantitative structure analysis for unknown nano-crystals.

Improvement of Measurement Accuracy by Correcting Systematic Error Associated with the X-ray Diffractometer (X-선 회절 장비의 기계적 오차 수정을 통한 분석 정확도 향상)

  • Choi, Dooho
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.18 no.10
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    • pp.97-101
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    • 2017
  • X-ray diffractometers are used to characterize material properties, such as the phase, texture, lattice constant and residual stress, based on the diffracted beams obtained from specimens. Quantitative analyses using X-rays are typically conducted by measuring the peak positions of the diffracted beams. However, the long-term use of the diffractomer, like any other machine, results in errors associated with the mechanical parts, which can deteriorate the accuracy of the quantitative analyses. In this study, the process of correcting systematic errors in the $2{\theta}$ range of $30{\sim}90^{\circ}$ is discussed, for which strain-free Si powders from NIST were used as the standard specimens. For the evaluation of the impact of such error correction, we conducted a quantitative analysis of the true lattice constant for tungsten thin films.

Effects of $Y_2O_3$ Addition on the Microstructure and Electrical Property of $TiO_2$-excess $BaTiO_3$

  • Kim, Jong-Han;Han, Young-Ho
    • Proceedings of the Korean Powder Metallurgy Institute Conference
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    • 2006.09b
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    • pp.1095-1096
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    • 2006
  • When $Y_2O_3$ was added to Ti-excess $BaTiO_3$ ((Ba+Y)/Ti =1), the area occupied by $Y^{3+}$ ion was confirmed by its microstructure development, electrical conductivity behavior and lattice constant. Grain growth inhibition was observed when the content of donor dopant exceeded a critical value ($x{\approx}.0.01$) in $BaTiO_3+x(0.5Y_2O_3+TiO_2)$ system. A donor-doped behavior was observed at various Y contents ($0.2\sim3.0$ mol% Y) when $Y_2O_3$ was added to $TiO_2$-excess $BaTiO_3$. As Y content was increased, (002) and (200) peaks shifted to higher angles and the lattice constant (a and c axis) decreased gradually.

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Precipitation Behaviors of HgTe Nanoinclusions Formed in Thermoelectric PbTe: Initial Induced Lattice Mismatch, Theoretical Calculation and Experimental Verification (PbTe 열전재료에 형성된 HgTe 나노개제물의 석출거동: 초기 격자 불일치의 형성, 이론적 계산 및 실험적 증명)

  • Kim, Kyung-Ho;Kwon, Tae-Hyung;Park, Su-Han;Ahn, Hyung-Keun;Lee, Man-Jong
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.24 no.7
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    • pp.599-604
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    • 2011
  • A highly strained nanostructure comprising crystallographically aligned HgTe nanoinclusions and a surrounding PbTe matrix has been synthesized using a precipitation process of supersaturated HgTe-PbTe alloys. From the early precipitation stage, HgTe nanoinclusions take disk shape, which is transformed from initial HgTe nuclei, although there is no lattice constant difference of the two end components at standard state. As a primary reason for the morphological transformation of the initial spherical HgTe nuclei to HgTe nanodisks, the induced lattice mismatch is suggested. On the condition that the HgTe nanodisks maintain perfect coherent nature with PbTe matrix, the stress-free lattice constant of constrained HgTe nanodisks has been calculated based on the defined concept of the strain-induced tetragonality, the linear elasticity and the actual measurement in HRTEM images.

The relation between optical diffraction pattern and domain size in blue phase

  • Lee, Ho-Hyun;Kim, Jong-Hyun;Kikuchi, H.
    • 한국정보디스플레이학회:학술대회논문집
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    • 2009.10a
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    • pp.942-944
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    • 2009
  • Blue phase shows several different reflection colors from the randomly oriented domains and crystal direction. Also there are variations in the size of domains. The domain size is dependent on the temperature gradient. With smaller cooling rate of temperature, the domain size was increased compared with rapid cooling. With injection of light of specific wavelength, we find that the diffraction patterns were occurred around the light spot in the cell of blue phase. It was supposed to be from the matching of the phase retardation and domain size. However, actually the diffraction pattern is reflecting the lattice structure in double twist of the blue phase. The lattice constant from the radius of diffraction patterns shows very similar one from the reflection spectrum, which indicates the internal lattice constant in double twist of the blues phase.

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The Theory of the One-Dimensional Lattice Defects

  • Jhon, Mu-Shik;Kim, Shoon-Kyung
    • Journal of the Korean Chemical Society
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    • v.15 no.4
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    • pp.165-169
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    • 1971
  • A general method of calculating the frequency shift due to lattice defects is developed for a one dimensional lattice with an arbitrary number of lattice points. The method is based on the Fourier transform of the equation of motion. It is shown that the frequency spectrum is determined by the roots of 5${\times}$5 secular equation, the coefficients of which depend on defects in the mass and the force constant as well as the number of the lattice points. For the limiting case of infinite lattice, the dimension of the secular equation reduces to three and the result agrees with that of Montroll and Potts.

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Variation of Lattice Constant in Ni-W and Ni-W-Cu Alloys for YBCO Coated Conductor (YBCO 초전도 박막 선재용 Ni-W 및 Ni-W-Cu 합금의 격자상수 변화)

  • Kim Min-Woo;Jung Kyu-Dong;Jun Byung-Hyuk;Kim Hyoung-Seop;Kim Chan-Joong
    • Progress in Superconductivity
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    • v.7 no.1
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    • pp.64-68
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    • 2005
  • We fabricated Ni-based alloy substrates for YBCO coated conductor using powder metallurgy. Tungsten and copper were selected as alloy elements due to their mutual solubility to the base element of nickel. The alloying elements were mixed with nickel using ball milling and dried in air. The powder mixtures were packed in a rubber mold, cold isostatic pressed 200 MPa and made into rods. The compacted rods were sintered at $1150^{\circ}C$ for 6 hours for densification. It was confirmed by neutron diffraction experiment that W and Cu atoms made complete solid solution with Ni. Lattice constant of nickel alloy increased by $0.004{\AA}$ for 1at. $\%$ W in Ni-W alloy, $0.0006{\AA}$ for 1 at. $\%$ Cu in Ni-W-Cu alloy.

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