• Proceedings of the Korean Magnestics Society Conference
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• 2008.12a
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• pp.103.2-103.2
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• 2008

• Current Photovoltaic Research
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• v.1 no.2
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• pp.109-114
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• 2013

$Cu_2ZnSnS_4$ (CZTS) nanoparticles were synthesized by a solvothermal method using copper (II) acetate, zinc acetate, tin chloride, and sulfur in diethylenetriamine solvent. Binary sulfide particles such as CuS, ZnS, SnS, and $SnS_2$ were obtained at $180^{\circ}C$; single-phase CZTS nanoparticles were obtained at $280^{\circ}C$. CZTS nanoparticles with spherical shape and grain size of 40 to 60 nm were obtained at $280^{\circ}C$. In the middle of 180 and $280^{\circ}C$, CZTS and ZnS phases were found. The time variation of reaction at $280^{\circ}C$ revealed that an amorphous state formed first instead of binary phases and then the amorphous phase was converted to crystalline CZTS state; it is different reaction path way from conventional solid-state reaction path of which binary phases react to form CZTS. CZTS films deposited and annealed from single-phase nanoparticles showed porous microstructure and poor adhesion. This indicates that a combination of CZTS and other flux phase is necessary to have a dense film for device fabrication.

• Transactions on Electrical and Electronic Materials
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• v.18 no.5
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• pp.261-264
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• 2017

$Ni_{0.79}Co_{0.15-x}Cu_xMn_{2.06}O_4$ ($0{\leq}x{\leq}0.09$) thick films were fabricated using the conventional solid-state reaction method and screen-printing method. Structural and electrical properties of specimens based on the amount of Cu were observed in order to investigate their applicability in the infrared detector. All specimens showed a single spinel phase with a homogeneous cubic structure. As the amount of Cu increased, the average grain size increased and was found to be approximately $5.01{\mu}m$ for the $Ni_{0.79}Co_{0.06}Cu_{0.09}Mn_{2.06}O_4$ specimen. The thickness of all specimens was approximately $55{\sim}56{\mu}m$. As Cu content increased, the resistivity and TCR properties at room temperature decreased, and these values for the $Ni_{0.79}Co_{0.06}Cu_{0.09}Mn_{2.06}O_4$ specimen were $502{\Omega}-cm$ and $-3.32%/^{\circ}C$, respectively. The responsivity and noise properties decreased with an increase in Cu content, with the specimen with a Cu content of x=0.09 showing 0.0183 V/W and $5.21{\times}10^{-5}V$, respectively.

• Transactions of the Korean hydrogen and new energy society
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• v.27 no.3
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• pp.270-275
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• 2016

A simple solid state incorporation method was employed in order to incorporate Pd nanocatalyst into a Nafion film for polymer electrolyte membrane fuel cell (PEMFC) via the reduction of palladium (II) bis (acetylacetonate), $Pd(acac)_2$. It was sublimed, penetrated into Nafion film and then reduced to Pd nanoparticles simultaneously in a glass reactor of N2 atmosphere at $180^{\circ}C$ for 1, 3 and 5 min. This reaction was took place without any reducing agent and any solvent. The morphology of the Pd nanoparticles was observed by transmission electron microscopy (TEM), and Pd distribution was analyzed by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). And 23% modification of tensile strength of Pd/Nafion composite film was measured by universal testing machine and I-V curve was estimated by using a unit cell with $5{\times}5cm^2$ active area.

• Journal of the Korean Ceramic Society
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• v.21 no.2
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• pp.165-173
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• 1984

It is desirable to establish reliable synthetic methods for electro-ceramic materials. To synthesize $SrTiO_3$ in this study direct solid state reactions and wet chemical processes were used. Previous study of $SrTiO_3$ synthesis included oxalated-method($SrTiO(C_2O_4)_2$.$4H_2O$) co-precipitation$(SrCO_3+TiO(OH)_2)$ and direct solid state reaction$(SrCO_3+TiO(OH)_2)$ The methods in question lead to intermediate inclusion during the reactions and less controllable in particle sizes of $SrTiO_3$. To obtain highly pure $SrTiO_3$ so-called "direct wet process method" was added in this investigation. In the study the "direct wet process" was for the first time applied to synthesize chemically pure and fine particle $SrTiO_3$. $SrCl_2$ and $TiCl_4$<\ulcornerTEX> at KOH solution at room temperature to 10$0^{\circ}C$ precipitated $SrTiO_3$ The particle size increased as temperature increased.mperature increased.

• Journal of the Korean Ceramic Society
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• v.40 no.4
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• pp.365-370
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• 2003

The phase development process of $Ba_2$ $Ti_{9}$ $O_{20}$ ceramics is not clearly known and frequently accompanies second phases which deteriorate dielectric properties. In synthesizing $Ba_2$ $Ti_{9}$ $O_{20}$ ceramics, in order to trace the reaction sequence during conventional solid-state reaction in BaO-Ti $O_2$ system, different barium sources of BaC0$_3$ and BaTi0$_3$ precursor were used as starting materials. From the analysis of XRD patterns, different secondary phases could be identified depending on the barium source used, which might mean that the equilibrium phases in BaO-Ti $O_2$ system are very difficult to be synthesized. Because the BaTi0$_3$ precursor provides short diffusion paths of ions, the system revealed less secondary phases during solid state reaction. In synthesizing BaO-xSm$_2$0$_3$-4.5Ti0$_2$ system using different barium sources, different secondary phases were developed also. Microstructure and dielectric properties were examined and discussed in terms of secondary phase development.

• Korean Journal of Materials Research
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• v.22 no.9
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• pp.489-493
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• 2012

Green phosphors $K_2BaW_2O_8:Tb^{3+}$(1.0 mol%) were synthesized by solid state reaction method. Differential thermal analysis was applied to trace the reaction processes. Three endothermic values of 95, 706, and $1055^{\circ}C$ correspond to the loss of absorbed water, the release of carbon dioxide, and the beginning of the melting point, respectively. The phase purity of the powders was examined using powder X-ray diffraction(XRD). Two strong excitation bands in the wavelength region of 200-310 nm were found to be due to the ${WO_4}^{2-}$ exciton transition and the 4f-5d transition of $Tb^{3+}$ in $K_2BaW_2O_8$. The excitation spectrum presents several lines in the range of 310-380 nm; these are assigned to the 4f-4f transitions of the $Tb^{3+}$ ion. The strong emission line at around 550 nm, due to the $^5D_4{\rightarrow}^7F_5$ transition, is observed together with weak lines of the $^5D_4{\rightarrow}^7F_J$(J = 3, 4, and 6) transitions. A broad emission band peaking at 530 nm is observed at 10 K, while it disappears at room temperature. The decay times of $Tb^{3+}$ $^5D_4{\rightarrow}^7F_5$ emission are estimated to be 4.8 and 1.4 ms, respectively, at 10 and 295 K; those of the ${WO_4}^{2-}$ exciton emissions are 22 and 0.92 ${\mu}s$ at 10 and 200 K, respectively.

• Korean Journal of Materials Research
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• v.29 no.2
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• pp.116-120
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• 2019

We prepared $Y_3Al_5O_{12};Ce^{3+},Pr3^{+}$ transparent ceramic phosphor using a solid state reaction method. By XRD pattern analysis and SEM measurement, our phosphors reveal an Ia-3d(230) space group of cubic structure, and the transparent ceramic phosphor has a polycrystal state with some internal cracks and pores. In the Raman scattering measurement with an increasing temperature, lattice vibrations of the transparent ceramic phosphor decrease due to its more perfect crystal structure and symmetry. Thus, low phonon generation is possible at high temperature. Optical properties of the transparent ceramic phosphor have broader excitation spectra due to a large internal reflection. There is a wide emission band from the green to yellow region, and the red color emission between 610 nm and 640 nm is also observed. The red-yellow phosphor optical characteristics enable a high Color Rendering Index (CRI) in combination with blue emitting LED or LD. Due to its good thermal properties of low phonon generation at high temperature and a wide emission range for high CRI characteristics, the transparent ceramic phosphor is shown to be a good candidate for high power solid state white lighting.

• Electrical & Electronic Materials
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• v.9 no.1
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• pp.18-23
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• 1996

The molding pressure is also one of the important parameters in the preparation of HTSC materials by the solid state reaction method. In the present study, changes in structural, electrical and microstructural proper-ties with the molding pressure in YiB $a_{2}$C $u_{3}$ $O_{70{\delta}}$ superconductors have been performed. The investigated molding pressures were 0.5*10$^{3}$ N/c $m^{2}$, 1*10$^{3}$ N/c $m^{2}$, 2*10$^{3}$ n/c $m^{2}$ and 4*10$^{3}$ N/c $m^{2}$. As the molding pressure increased, the anisotropy of the crystal structure decreased and the grains have been grown preferentially in a c-axis direction. Since the size of the grain becomes larger with the decrease of the porosity, denser textures are formed. The results indicated that the critical current density is improved resulting from the enhanced densification due to higher molding pressure. When the molding pressure was between 1*10$^{3}$ N/c $m^{2}$ and 2*10$^{3}$ N/c $m^{2}$, while it did not affect the oxygen deficiency and Tc, the increase of the molding pressure affects remarkably on grain size and densification of the $Y_{1}$B $a_{2}$C $u_{3}$ $O_{7-{\delta}}$. When the molding pressure is larger than 2*10$^{3}$ N/c $m^{2}$, electrical proper-ties are independent on the molding pressure..

• Journal of the Korean Ceramic Society
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• v.31 no.9
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• pp.1030-1036
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• 1994

The ceramics in the system 0.5[Pb(Ni1/3Nb2/3)O3]-0.5[0.65PbTiO3-0.35PbZrO3] were prepared by conventional solid state reaction method, double calcined method (columbite precursor method) and flux method using NaCl-KCl. Amount of pyrochlore phase for the calcined powders, sintering charateristrics, dielectric and piezoelectric properties were then investigated. Sintering temperature was 1000~120$0^{\circ}C$ and in case of flux method, the amount of flux to oxide was 1 : 1 mole ratio. The dielectric and piezoelectric properties of ceramics prepared by double calcined method and flux method were found to be better than those by conventional method. It was also possible to lower sintering temperature and reduce the amount of pyrochlore phase either by double calcined method or flux method. But with increasing sintering temperature, the difference in characteristrics due to diffrent fabrication method gradually.