• Journal of Powder Materials
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• v.18 no.3
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• pp.256-261
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• 2011

In order to make a $Cu_2ZnSnSe_4$ (CZTSe) sputtering target sintered for solar cell application, synthesis of CZTSe compound by solid state reaction of Cu, Zn, Sn and Se mixed powders and effects of ball milling condition on sinterability such as ball size, combination of ball size, ball milling time and sintering temperature, was investigated. As a result of this research, sintering at $500^{\circ}C$ after ball milling using mixed balls of 1 mm and 3 mm for 72 hours was the optimum condition to synthesis near stoichiometric composition of $Cu_2ZnSnSe_4$ and to prepare sintered pellet with high density relatively.

• Korean Journal of Materials Research
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• v.14 no.12
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• pp.885-888
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• 2004

$BaMgAl_{10}O_{17}:Eu^{2+}$ for PDP blue phosphor was synthesized using SHS(Self-propagating High temperature Synthesis) method. While Al metal powder was oxidized in this combustion, $Eu_{2}O_3$ was reduced to Eu2+. Therefore the mole ratio of $Al/Al_{2}O_3$ is one of the most important variable of the reaction. When $Al/Al_{2}O_3$ is 2.5/3.75, it has not only appropriate temperature and reaction velocity, but also excellent luminescent property. The sample synthesized in this system has similar characteristics comparing to sample using conventional solid-state reaction.

• Journal of the Korean Ceramic Society
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• v.39 no.7
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• pp.617-621
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• 2002

Calcium aluminosulfate (3CaO.3Al$_2$O$_3$.CaSO$_4$or $C_4$A$_3$S) was prepared by chemical synthesis from the nitrate salts and aluminum sulfate. $C_4$A$_3$S was the main phase after calcination at 110$0^{\circ}C$. The specific surface areas after calcination at 110$0^{\circ}C$ and 130$0^{\circ}C$ were about 2.5 and 1.0 $m^2$/g, respectively. Hydration was investigated by XRD, DSC, SEM, EDS, conduction calorimetry and analysis of the liquid phase. Calorimetry showed that the induction period was longer than that of a sample prepared by conventional solid state sintering and this was attributed to the formation of amorphous coatings in abundance of $Al_2$O$_3$ and SO$_3$. Crystalline hydration products, principally calcium monosulfoaluminate hydrate and Al(OH)$_3$, appeared subsequently.

• Journal of the Korean Electrochemical Society
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• v.8 no.1
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• pp.42-46
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• 2005

It has been known that the synthesis of the cathode materials for the lithium rechargeable batteries by the sol-gel process has many advantages over the conventional solid-state method. It has been, however, a continuing issue that new additional steps should be introduced to commercialize this process. In this work, spray drying was introduced to the existing sol-gel process as a continuous mass production method of the pre-heat treatment precursor materials. The precursors of $LiCoO_2$ and $LiNi_{0.8}Co_{0.2}O_2$ were continuously produced through spray drying from the solution containing stoichiometric amount of lithium, cobalt, and nickel sources as well as a chelating agent. The process variables, such as pH of the starting solution, spray drying conditions, and calcination conditions were optimized. The XRD pattern for the synthesized material indicated a good crystallinity with a layered structure.

• Korean Journal of Materials Research
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• v.30 no.2
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• pp.74-80
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• 2020

Synthesis of composite powders for the Fe₂O₃-Zn system by mechanical alloying (MA) has been investigated at room temperature. Optimal milling and heat treatment conditions to obtain soft magnetic composite with fine microstructure were investigated by X-ray diffraction, differential scanning calorimetry (DSC) and vibrating sample magnetometer (VSM) measurement. It is found that α-Fe/ZnO composite powders in which ZnO is dispersed in α-Fe matrix can be obtained by MA of Fe₂O₃ with Zn for 4 hours. The change in magnetization and coercivity also reflects the details of the solid-state reduction process of hematite by pure metal of Zn during MA. Densification of the MA powders was performed in a spark plasma sintering (SPS) machine at 900 ~ 1,000 ℃ under 60 MPa. Shrinkage change after SPS of sample MA'ed for 5 hrs was significant above 300 ℃ and gradually increased with increasing temperature up to 800 ℃. X-ray diffraction results show that the average grain size of α-Fe in the α-Fe/ZnO composite sintered at 900 ℃ is in the range of 110 nm.

• Bulletin of the Korean Chemical Society
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• v.35 no.10
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• pp.2917-2921
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• 2014

Cerium-activated yttrium aluminate ($Y_3Al_5O_{12}:Ce^{3+}$) exhibiting a garnet structure has been widely utilized in the production of light emitting diodes (LEDs) as a yellow emitting phosphor. The commercialized yttrium aluminum garnet (YAG) phosphor is typically synthesized by a solid-state reaction, which produces irregular shape particles with a size of several tens of micrometers by using the top-down method. To control the shape and size of particles, which had been the primary disadvantage of top-down synthetic methods, we synthesized YAG:Ce nanoparticles with a diameter of 500 nm using a coprecipitation method under the atmospheric pressure without the use of template or special equipment. The precursor particles were formed by refluxing an aqueous solution of the nitrate salts of Y, Al, and Ce, urea, and polyvinylpyrrolidone (55 K) at $100^{\circ}C$ for 12 h. YAG:Ce nanoparticles were formed by the calcination of precursor particles at $1100^{\circ}C$ for 10 h under atmospheric conditions. The phase identification, microstructure, and photoluminescent properties of the products were evaluated by X-ray powder diffraction, scanning electron microscopy, absorption spectrum and photoluminescence analyses.

• Journal of Magnetics
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• v.14 no.2
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• pp.62-65
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• 2009

The multiferroic $BiFeO_3$ has been investigated extensively in both thin film and ceramic form. However, the synthesis of a perfect sample with high resistivity is a prerequisite for examining its properties. This paper reports the synthesis of multiferroic $BiFeO_3$ along with its structural, electrical and magnetic properties in ceramic form. Polycrystalline ceramic samples of $BiFeO_3$ were synthesized by solid-state reaction using high purity oxides and carbonates. The formation of a single-phase compound was confirmed by x-ray diffraction and its lattice parameters were determined using a standard computer program. The microstructural studies and density measurement confirmed that the prepared samples were sufficiently dense for an examination of its electrical and magnetic properties. The dc electrical conductivity studies show that the sample was resistive with an activation energy of ${\sim}0.81\;eV$. The magnetization measurement showed a linear ($M{\sim}H$) curve indicating antiferromagnetic characteristics.

• Journal of Powder Materials
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• v.20 no.3
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• pp.221-227
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• 2013

$TiB_2$-reinforced iron matrix composite (Fe-$TiB_2$) powder was in-situ fabricated from titanium hydride ($TiH_2$) and iron boride (FeB) powders by the mechanical activation and a subsequent reaction. Phase formation of the composite powder was identified by X-ray diffraction (XRD). The morphology and phase composition were observed and measured by field emission-scanning electron microscopy (FE-SEM) and energy-dispersive X-ray spectroscopy (EDS), respectively. The results showed that $TiB_2$ particles formed in nanoscale were uniformly distributed in Fe matrix. $Fe_2B$ phase existed due to an incomplete reaction of Ti and FeB. Effect of milling process and synthesis temperature on the formation of composite were discussed.

• Bulletin of the Korean Chemical Society
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• v.33 no.6
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• pp.1929-1933
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• 2012

Two cobalt(II) compounds $[Co(2,2{^\prime}-bipy)(H_2O)_2(SO_4)]_n$ (1) and $[Co_2(2,2^{\prime}-bipy)_2(btec)(H_2O)_6]{\cdot}2H_2O$ (2) (2,2'-bipy = 2,2'-bipyridine, $H_4btec$ = 1,2,4,5-benzenetetracarboxylic acid), have been simultaneously synthesized by a one-pot slow solvent evaporation reaction. Their structures were determined by single-crystal X-ray diffraction and further characterized by X-ray powder diffraction (XRPD), IR, elemental and thermogravimetric analysis (TGA). The structural analysis reveals that compound 1 exhibits an infinite 1D chain structure with the octahedral Co(II) centers bridging by the tetrahedral ${\mu}_2-SO{_4}^{2-}$ ligands, while compound 2 possesses a dinuclear $Co_2(2,2^{\prime}-bipy)_2(btec)(H_2O)_6$ unit and the two adjacent octahedral Co(II) ions are linked by the bismonodentately coordinated btec ligand. Additionally, compound 2 exhibits blue fluorescent emission in the solid state at room temperature.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.26 no.4
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• pp.150-154
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• 2016

Method for synthesizing a $K_2Ti_6O_{13}$ whisker is a solid-state method, hydrothermal synthesis method, calcination method, flux method, slow-cooling method, melting method, kneading-drying-calcination method, sol-gel method etc. $K_2Ti_6O_{13}$ whisker have been synthesized by a flux method. The average size and distribution of the synthesized $K_2Ti_6O_{13}$ whisker can be controlled by a kind of potassium precursors and reaction temperature and time. The average size of the synthesized $K_2Ti_6O_{13}$ whisker was about in the size range of 500 nm to $2{\mu}m$. The effect of synthesis parameters, such as the molar ratio of KOH to $TiO_2$, pH, reaction temperature and time, are discussed. The synthesized $K_2Ti_6O_{13}$ whisker were characterized by x-ray diffraction analysis (XRD), field emission scanning electron microscopy (FE-SEM).