• Journal of the Korean Physical Society
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• 제73권10호
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• pp.1541-1545
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• 2018

We study lattice thermal conductivity of $Sb_2Te_3$ using molecular dynamics simulations. The interatomic potentials are fitted to reproduce total energy and elastic constants, and phonon properties calculated using the potentials are in reasonable agreement with first-principles calculations and experimental data. Our calculated lattice thermal conductivities of $Sb_2Te_3$ decrease with temperature from 150 K to 500 K. The in-plane lattice thermal conductivity of $Sb_2Te_3$ is higher than cross-plane lattice thermal conductivity of $Sb_2Te_3$, as in the case of $Bi_2Te_3$, which is consistent with the anisotropy of the elastic constants.

• 한국전기전자재료학회논문지
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• 제14권3호
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• pp.257-262
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• 2001

Single crystalline films of La doped YIG(yttrium iron garnet) were grown by the liquid phase epitaxy. The lattice constants of films obtained by DCD(double crystalline diffractometer) measurement increased with increasing La contents in films. In particular, lattice constants of films grown wiht Y/La=20 solution were nearly same as those of GGG (gadolinium gallium garnet) substrate. The saturation magnetization measured with VSM (vibrating sample magnetometer) was about 1750Gauss which is the same as that of pure YIG irrespective of La contents in films. FMR(ferromagnetic resonance) linewidth of La doped YIG was smaller than that of pure YIG. Since appropriate La doping decreases the lattice mismatch between film and substrate, the FMR linewidth was Y/La=20 in this experiment.

• International Journal of Air-Conditioning and Refrigeration
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• 제10권1호
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• pp.1-9
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• 2002

Effects of temperature coefficients fur dielectric constants on transient reflectances and thermal responses have been investigated for a metal(gold) thin-film during ultrashort pulse laser heating. Heating processes are simulated using the conventional conduction model(parabolic one-step, POS), the parabolic tow-step model(PTS), the hyperbolic two-step model(HTS). Results fro the HTS model are very similar to those from the PTS model, since the laser heating time in this study is considerably greater than the electron relaxation time. PTS and HTS models, however, result in completely different temperature profiles from those obtained by the POS model due to slow electron-lattice interactions compared to laser pulse duration. Transient reflectances are directly estimated from the linear relationship between electron temperature and complex dielectric constants, while conventional approaches assume that the change in reflectances is proportional to that in temperatuer. Reflectances at the front surface vary considerably for various dielectric constants, while those at the rear surface remain unchanged relatively.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
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• pp.620-620
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• 2013

When $MoS_2$ is thinned to single layer (1L), photoluminescence (PL) quantum yield drastically increases due to emergence of direct band gap. A recent theory predicts that the electronic structure of 1L $MoS_2$ is very sensitive to its lattice constants. We investigated the response of 1L $MoS_2$ to biaxial tensile strain using spatially resolved PL and Raman spectroscopy. Changes in the lattice constants were monitored by the Raman frequency of the in-plane ($E^1{_2g}$) mode. Systematic correlations between PL and Ramanspectral features, revealed in the preliminary results, will be further tested with samples on other substrates and against thermal stress. The results will also be discussed in regard to the theory which predicts that 1L $MoS_2$ becomes an indirect semiconductor at small tensile strain and turns metallic when further extended.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1996년도 춘계학술대회 논문집
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• pp.1.1-5
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• 1996

Structural characteristics in Se thin film fabricated by EBE method had been studied. Se thin film was deposited with noncrystalline until substrate temperature of 100$^{\circ}C$. But Se film was grown with monoclinic at substrate temperature of over 150$^{\circ}C$. Lattice constants of it were as follow: a=12.76[${\AA}$], b=9.15[${\AA}$], c=10.4[${\AA}$]. 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. Lattice constants of it were as follow: a=4.27[${\AA}$], c=4.83[${\AA}$].

• 한국세라믹학회지
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• 제31권1호
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• pp.47-54
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• 1994

The fundamental studies for exploit natural resources was investigated on Uljin pottery stones that estimated the amount of mineral deposits at 350 million tons. The results obtained are as follows; In the chemical composition of Uljin pottery stones the amount of Al2O3 are a little compared with other pottery stones and that of Na2O and K2O are a large. Fe2O3 content is lower than 0.3 wt%, thus whiteness of its is 83. The major minerals composition of Uljin pottery stones are quartz and feldspar mineral. The refractoriness (SK) of its is 14. Lattice constants of quartz in Uljin pottery stones are 4.8865 $\AA$ in a-axis and 5.3852 $\AA$ in c-axis. Lattice constants were expanded by HCl treatment and sintering. Microstructures of Uljin pottery stones are linked up with the crystal particles under 10 microns in size.

• Bulletin of the Korean Chemical Society
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• 제6권6호
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• pp.344-347
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• 1985

Perovskite type oxides of $SrTiO_3,SrZrO_3,and\;SrTi_{1-x}Zr_xO_3$ have been systematically synthesized at $1250^{\circ}C$and $1550^{\circ}C$ with specimens containing additions of up to x=0.9 of zirconium by solid state reactions and characterized by X-ray diffraction. X-ray diffraction studies showed that the compound $SrTi_{1-x}Zr_xO_3$ has cubic structure. The lattice paramters of $SrTi_{1-x}Zr_xO_3$ solid solutions obey the Vegard's law and fairly large increase in volume can acompany the formation of this solution with increasing Zr content(X). Assuming the lattice constants of perovskite type compounds $A(B_{1-x}B'_x)O_3$where $B_{1-x}B'_x$ is $Ti_{1-x}Zr_x$, to be a linear function of the ionic radii of B and B' ions, the disordered ion pair of $Ti^{4+}$and $Zr^{4+}$ was verified from the lattice constants of a series compounds varying x=0,0.05, 0.25, 0.5, 0.75, 0.9, and 1.0 with known isovalent pairs.

• Journal of Mechanical Science and Technology
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• 제17권12호
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• pp.2034-2041
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• 2003

This study introduced a lattice Boltzmann computational scheme capable of modeling thermo hydrodynamic flows with simpler equilibrium particle distribution function compared with other models. The equilibrium particle distribution function is the local Maxwelian equilibrium function in this model, with all the constants uniquely determined. The characteristics of the proposed model is verified by calculation of the sound speeds, and the shock tube problem. In the lattice Boltzmann method, a thermal fluid or compressible fluid model simulates the reflection of a weak shock wave colliding with a sharp wedge having various angles $\theta$$\sub$w/. Theoretical results using LBM are satisfactory compared with the experimental result or the TVD.

• Nuclear Engineering and Technology
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• 제7권2호
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• pp.107-118
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• 1975

천이금속을 구성하고 있는 성분 이온을 변형가능한 이온으로 취급함으로써 크로미움, 몰리브데늄 및 텅스텐의 격자진동을 전자각 모텔에 외해 수식화했다. 이 모델은 전하에 대한 두 변수와 다섯 개의 힘상수를 모두 합쳐 7개의 모텔상수를 포함하고 있으며 이들의 수치는 금속의 탄성 계수에 관한 자료와 중성자 산란 실험에 의해 측정된 격자진동의 특성 주파수 값과 일치하도록 하여 결정했다. 한편 전자각 모델은 Cr, Mo 및 W등 세 금속의 성파 확산곡선, 주파수 분포함수 및 비열을 계산하는데 응용하였고 그 결과를 실험치와 비교하였다. 이로부터 전자각 모델로도 천이금속의 격자진동에 대한 특성을 만족스럽게 설명할 수 있다는 것을 알아내었다. 또한 다른 격자 모델과의 비교를 통하여 전자각 모델의 유용성을 검토했다.

• 한국결정성장학회지
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• 제8권1호
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• pp.91-96
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• 1998

Huntite 구조를 갖는 borate결정의 격자상수($a_0$ 및 $c_0$ ) 산출을 위해 특정관계를 갖는 계산식을 도출하였다. 이를 위해 서로 다른 28종류의 조성을 갖고 있는 결정을 사용하였다. 이와 같은 계산식은 huntite 구조내에 위치하는 이온의 평균 반경을 함수로 하여 미지의 조성을 갖고 있는 결정으로부터 격자상수를 예상하는데 사용될 수 있다.