• Journal of the Korean Crystal Growth and Crystal Technology
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• v.31 no.5
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• pp.197-202
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• 2021

Synthesis of Z-type hexaferrite Ba₃Co₂Fe₂₄O₄₁ (Ba₃Z) and Ba_1.5La_1.5Co₂Fe₂₄O₄₁ (Ba_1.5La_1.5Z) powders were tried using molten salt synthesis after primary calcination. Ba₃Z calcined at 1000℃ was formed with both M-type and Y-type hexaferrite, and then Z-type was obtained when sintered with molten salt at 1150℃ and 1200℃. In the case of Ba_1.5La_1.5Z calcined at 1000℃, however, M-type hexaferrite, CoFe₂O₄ (Spinel phase), and LaFeO₃ were synthesized. As a result, Z-type hexaferrite was not synthesized after sintering with molten salt. In addition, the aspect ratio of the particles decreased as the sintering temperature increased with molten salt synthesis. To obtain a single-phase Ba_1.5La_1.5Z with a high aspect ratio, it is expected the raw materials have to calcine below the temperature of a spinel phase formation before sintering with molten salt.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.18 no.4
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• pp.155-159
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• 2008

In this work, we report synthesis of free-standing ZnO/Zn core-shell micro-polyhedrons using metal Zn pellets as a source material by the thermal chemical vapor deposition process. Scanning and transmission electron microscopy measurements were introduced to investigate morphologies and structural properties of as-grown ZnO/Zn core-shell micro-polyhedrons. It was found that micro-polyhedrons were composed of inner single-crystalline metal Zn surrounded by single-crystalline ZnO nanorod arrays. The inner single crystalline metal Zn with micro-scale diameter has a hexagonal crystal structure. Diameter and height of ZnO nanorods covering the metal Zn surface are below 10 nm and 100 nm, respectively. It was also confirmed that c-axis oriented ZnO nanorods are single crystalline with a hexagonal crystal structure.

• Journal of the Korean Ceramic Society
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• v.34 no.3
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• pp.249-256
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• 1997

The effect of process parameter of plasma assisted chemical vapor deposition (PACVD) on the variation of the ratio between cubic boron nitride (c-BN) and hexagonal boron nitride (h-BN) in the film was in-vestigated. The plasma was generated by electric power with the frequency between 100 and 500 KHz. BCl3 and NH3 were used as a boron and nitrogen source respectively and Ar and hydrogen were added as a car-rier gas. Films were composed of h-BN and c-BN and its ratio varied with the magnitude of process parameters, voltage of the electric power, substrate bias voltage, reaction pressure, gas composition, sub-strate temperature. TEM observation showed that h-BN phase was amorphous while crystalline c-BN par-ticle was imbedded in h-BN matrix in the case of c-BN and h-BN mixed film.

• Korean Journal of Materials Research
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• v.7 no.6
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• pp.517-521
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• 1997

고분해능 전자현미경과 컴퓨터 이미지 시뮬레이션이 La이 첨가되고 또한 첨가되지 않은 Pb(Mg/ sub 1/3/Nb$_{2}$3/)O$_{3}$고용체의 미세구조를 연구하기 위해서 사용되었다. 불규칙격자 영역의 격자 이미지는 정방정 형태와 유사 육방정 형태를 각각 보였다. 규칙격자 영역에서 Mg과 Nb의 비화학양론적인 규칙격자 구조 현상이 <111>방향에 따라 관찰되었다. 실험 격자 이미지와 컴퓨터 시뮬레이션 이미지의 비교로부터, 규칙격자 구조를 가지는 영역의 장거리 규칙도는 0.2-0.7의 값을 가지고 있었고, 또한 규칙격자는 (NH$_{4}$)$_{3}$FeF$_{6}$결정구조를 가지고 있었다. 작은 값의 장거리 규칙도를 가지는 규칙격자를 가지는 영역에서, 변형률 파형이 관찰되지 않았다. 이것은 대부분 두 양이온이 그들의 위치에 있기 때문에, 원자 변위가 없었기 때문이다.

• Applied Microscopy
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• v.28 no.3
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• pp.415-424
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• 1998

The dependency of long-range order parameter on the ordered structure of $Pb(Mg_{1/3}Nb_{2/3})O_3$ solid solutions has been investigated by means of computer simulations of high-resolution lattice images. The computer image simulations were performed by the multislice method in a wide range of sample thicknesses, defocusing values, and long-range order parameters. It was found that the lattice images of the ordered structures were predominantly dependent on the long-range order parameter, The lattice images in a complete ordered structure showed a pseudo-hexagonal pattern. As the order parameter decreases, the simulated images changed slowly from a pseudo-hexagonal pattern to a rectangular pattern. The lattice images in a complete disordered structure showed a rectangular pattern. Also, the simulated images of the $Pb(Mg_xNb_{1-x})O_3$ with different Mg:Nb ratios obtained at a given long-range order parameter were basically the same patterns, irrespective of Mg and Nb compositions.

• Korean Journal of Crystallography
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• v.1 no.1
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• pp.49-56
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• 1990

The crystallizied Inactions of the two metastable phases in the glasses of plagioclase compositions were estimated by x-ray diffraction method. The orthorhombic metastable phase is easily drystaliized in the composition range of 70 to 80 mol% of albite, whereas the hexagonal metastable phase is mostly crystallized in the anonhite-rich side. For the purpose of refining the orthorhombic metastable structure some single crystal fragments of the composition Na,17ca‥‥All Isi2 nn were separated Som the crystallized glasses. The cell parameters of this crystal are a=8.237(1)A. b=8.644(1)A c=4.818(1)A. The space group of this crystal is Pn,2, Final atomic coordinates give R value of 0.040 and Rw of 0.028 with anisotropic thermal parameters. The position of Na and Ca atoms statistically distributed is splitted in two points with the occupancy of 0.5. The Si and Al atoms are statistically distributed in the six-membered ring of the Immm-type framework.

• Journal of the Korean Magnetics Society
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• v.4 no.2
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• pp.114-121
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• 1994

A $Ba_{2}Co_{2-x}Zn_{x}Fe_{12}O_{22}(x\;=\;0.0~2.0,\;Co_{2-x}Zn_{x}Y)$ powder was prepared by a oxidation--coprecipitation method and sintered at $1150~1250^{\circ}C$ for 4 hours. The microstructures and magnetic properties(saturation magnetization, Curie temperature), complex permeability of sintered body were measured As increasing Zn content from x = 0 to 2.0 in $Co_{2-x}Zn_{x}Y$, the real value of complex permeased from 7 GHz to 1 GHz. Because of resonance in few GHz range, Y-type hexagonal ferrite is rmre applicalble than spinel ferrite in high frequency range, and more research would be necessary to find the mechanism of the second resonance observed in higher frequency.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07b
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• pp.830-833
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• 2002

최근 나노 구조 (nano structure)를 만들기 위한 시도 중 하나로서 스스로 조직화(self organization)하여 나노 구조를 형성하는 물질을 나노 소자 제작을 위한 형틀 (template)로 이용하려는 시도가 활발히 진행되고 있다. 이러한 물질로서 주목을 받고있는 것 중 하나가 전해질 용액에서 알루미늄을 양극산화(anodization) 시켰을 때 형성되는 다공성 알루미나 박막이다. 본 연구에서는 고 순도 알루미늄을 기계적으로 연마(mechanical polishing)하고 공기 분위기에서 어닐링 (annealing)하여 알루미늄을 재결정화(recrystallization) 시키고 인가 전압이 40 V인 정 전압하에서 0.3 M의 수산(oxalic acid)을 전해질로 사용하면서 양극산화를 수행하여 평균 직경이 65 nm인 고도로 배열된 육방밀집구조의 나노 다공성 박막을 제작하였다. 또한 같은 방향의 육방밀집 배열은 크기가 수 ${\mu}m$인 영역(grain)을 형성하고 있었으며, 평균적인 pore의 밀도는 $1.1{\times}10^{10}/cm^2$였다.

• Korean Journal of Materials Research
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• v.10 no.9
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• pp.648-655
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• 2000

Synthesis of the crystalline film was investigated under the diamond growth condition with altering the addition of the nitrogen from 0% to 95%. With increasing the nitrogen concentration, surface morphology of the film was changed from the diamond film with {100} growth plane to the non-faceted diamond film with nano-scale grains. It also showed that the deposition of the diamond film could be synthesized using only methane and nitrogen gases without hydrogen gas. Separated particles with diamond structure showed an octahedral shaped I the nitrogen ranges between 30% and 80%, and newly formed hexagonal crystals are observed when substrate temperature with diamond structure, however, also identify that the hexagonal crystal was SiCN composite composed of Si, C and N atoms.

• Journal of the Korean Magnetics Society
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• v.6 no.2
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• pp.73-79
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• 1996

Y-type hexagonal ferrites$(Ba_{2}Me_{2}Fe_{12}O_{22}:Me=transition metal)$ have promising electromagnetic properties in GHz range. Co and Zn are good candidates for the transition metal. To understand their role on the properties, it is thus necessary to study the ion(s) distribution in that complex Y-type hexagonal ferrite structure. The authors report Mossbauer spectroscopic results from very reliable samples, which has been extensively characterized by chemical analysis, Rietveld analysis of X-ray diffraction patterns, and magnetic property measurements. Analyzing two samples, $Co_{2}Y$ and $Co_{1.6}Zn_{0.4}Y$, conclusions are made as follow: (1) Co ions prefer the tetrahedral interstitial sites in the S-block $(6c_{IV})$ and the octahedral sites $(18h_{VI})$ at the interface of S- and T-block. (2) Partial substitution of Co with Zn (within the experimental range) does not disturb the Fe distribution.