• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.2
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• pp.90-94
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• 2016

In this work, [$Pb(Mg_{1/2}W_{1/2})_{0.03}(Ni_{1/3}Nb_{2/3})_x(Zr_{0.5}Ti_{0.5})_{0.97-x}O_3-BiFeO_3$] (x=0.02 to 0.12) composition ceramics were fabricated by the conventional soild state reaction method and their microstructure and piezoelectric properties were investigated according to PNN substitution. The addition of small amount of $BiFeO_3$, $Li_2CO_3$, and $CaCO_3$ were used in order to decrease the sintering temperature of the ceramics. The XRD (x-ray diffraction patterns) of all ceramics exhibited a perovskite structure. The sinterability of PMW-PNN-PZT-BF ceramics was remarkably improved using liquid phase sintering of $CaCO_3$, $Li_2CO_3$. However, it was identified from of the X-ray diffraction patterns that the secondary phase formed in grain boundaries decreased the piezoelectric properties. According to the substitution of PNN, the crystal structure of ceramics is transformed gradually from a tetragonal to rhombohedral phase. The x=0.10 mol PNN-substituted PMW-PNN-PZT-BF ceramics sintered at $920^{\circ}C$ showed the optimum values of piezoelectric constant($d_{33}$), piezoelectric figure of merit($d_{33{\cdot}}g_{33}$), planar piezoelectric coupling coefficient($k_p$) and density : $d_{33}=566$ [pC/N], $g_{33}=29.28[10^{-3}mV/N]$, $d_{33{\cdot}}g_{33}=16.57[pm^2/N]$, $k_p=0.61$, density=7.82 [$g/cm^3$], suitable for duplex ultrasonic sensor application.

• Korean Journal of Materials Research
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• v.20 no.8
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• pp.429-433
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• 2010

In this study, activated carbon (AC) as a carbon source was modified with different concentrations of cobalt chloride ($CoCl_2$) to prepare a Co-AC composite, and it was used for the preparation of Co-AC/$TiO_2$ composites with titanium oxysulfate (TOS) as the titanium precursor. The physicochemical properties of the prepared Co-AC/$TiO_2$ composites were characterized by $N_2$ adsorption at 77 K, X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive X-ray (EDX) analysis. The photocatalytic treatments of organic dyes were examined under an irradiation of visible light with different irradiation times. $N_2$ adsorption data showed that the composites had decreased surface area compared with the pristine AC, which was $389\;m^2/g$. From the XRD results, the Co-AC/$TiO_2$ composites contained a mixturephase structuresof anatase and rutile, but a cobalt oxide phase was not detected in the XRD pattern. The EDX results of the Co-AC/$TiO_2$ composites confirmed the presence of various elements, namely, C, O, Ti, and Co. Subsequently, the decomposition of methylene orange (MO, $C_{14}H_{14}N_3NaO_3S$) and rhodamine B (Rh.B, $C_{28}H_{31}ClN_2O_3$) in an aqueous solution, respectively, showed the combined effects of an adsorption effect by AC and the photo degradation effect by $TiO_2$. Especially, the Co particles in the Co-AC/$TiO_2$ composites could enhance the photo degradation behaviors of $TiO_2$ under visible light.

• Korean Chemical Engineering Research
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• v.44 no.2
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• pp.193-199
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• 2006

The catalytic oxidation of toluene over $-Al_2O_3$ supported copper-manganese oxide catalysts in the temperature range of $160-280^{\circ}C$ was investigated by employing a fixed bed flow reactor. The catalysts were characterized by BET, scanning electron microscopy (SEM), temperature-programmed reduction(TPR), temperature-programmed oxidation(TPO), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction(XRD) techniques. Catalytic oxidation of toluene was achieved at the below $280^{\circ}C$, and the optimal content of copper and manganese in the catalyst was found to be 15.0 wt％Cu-10.0 wt％Mn. From the TPR/TPO and XPS results, the redox peak of 15 Cu-10 Mn catalyst shifted to the lower temperature, and the binding energy was shifted to the higher binding energy. Furthermore, It is considered that $Cu_{1.5}Mn_{1.5}O_4$ is superior to Mn oxides and CuO in the role as active factor of catalysts from the XRD results and also catalytic activities are dependent on the redox ability and high oxidation state of catalysts.

• Journal of the Korean Ceramic Society
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• v.30 no.6
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• pp.499-509
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• 1993

Structures of hematite(${\alpha}$-Fe2O3), Ba-ferrite(BaFe12O19) and Zn2Y(Ba2Zn2Fe12O22) were studied by powder X-ray diffraction(XRD) method. Powder XRD patterns of the ferrites were analyzed with the Rietveld method, and the final refined R-factors were RWP<0.01 and RI<0.03. The lattice parameters refined with hexagonal crystal system were a=5.0342${\AA}$, c=13.746${\AA}$ for hematite, a=5.8928${\AA}$, c=23.201${\AA}$ for Ba-ferrite, and a=5.8763${\AA}$, c=43.567${\AA}$ for Zn2Y. In the hematite, the oxygen parameter is 0.3072 and the Fe-O distances in FeO6octahedron are 1.941${\AA}$ and 2.118${\AA}$, close to the single crystal data of Blake et al.. In the Ba-ferrite, the Fe atom in oxygen trigonal bipyramid is displaced 0.155${\AA}$ away from the BaO3 mirror plane into 4e position. In the Zn2Y, 75% of Zn is located at the oxygen terahedral site in S-block.

• Journal of the Korean Vacuum Society
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• v.12 no.S1
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• pp.7-9
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• 2003

Solid-state reactions in Ni/Si multilayered films (MLF) with an overall stoichiometry of $Ni_2Si$, NiSi and $NiSi_2$, induced by ion-beam mixing (IBM) and thermal annealing, were studied by using spectroscopic ellipsometry and magneto-optical spectroscopy as well as x-ray diffraction (XRD). The mixing was performed with Ar+ ions of an energy of 80 keV and a dose of $1.5 x\times10^{16}$ $Ar^+$/$\textrm{cm}^2$. It was shown that the IBM induces structural changes in the Ni/Si MLF, which cannot be detected by XRD but are confidently recognized by the optical method. A thermal annealing at 673 K of the Ni/Si MLF with an overall stoichiometry of NiSi and $NiSi_2$ causes formation of the first η -NiSi phase. The first trace for $NiSi_2$ phase on the background of NiSi one was detected by XRD after an annealing at 1073 K while, according to the optical results, $NiSi_2$ turns out be the dominant phase for the annealed Ni/Si MLF with an overall stoichiometry of $NiSi_2$.

• Applied Chemistry for Engineering
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• v.27 no.5
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• pp.543-545
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• 2016

Four different hydroxyapatites (HAP) were prepared by a solvothermal method under different pHs and solvent species. The synthesized hydroxyapatites were analyzed by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Four HAPs exhibited similar XRD patterns regardless of synthetic conditions. However, the morphology of hydroxyapatites was dependent of pH and solvent species under synthetic condition. The HAP prepared in pH 12 showed an elongated shape along the [001] direction compared to that prepared in pH 8. Also, the morphology of the HAPs synthesized in the presence of methanol and ethanol exhibited the more elongated hexagonal rod shape along the [001] direction with the high aspect ratio.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.31 no.5
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• pp.228-232
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• 2021

Ca_1-xZrO₃:xPr phosphor with perovskite structure was successfully synthesized by using skull melting method. The crystal structure, morphology and optical properties of synthesized phosphor were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), ultraviolet fluorescence reaction and photoluminescence. The XRD results indicated that single crystals of CaZrO₃:Pr³⁺ belongs to orthorhombic perovskite system. The synthesized phosphor could be excited by UV light (254 nm) and the emission spectra results indicated that green luminescence of CaZrO₃:Pr³⁺ due to charge transfer transition ³P₀ → ³H₄, ³P₁ → ³H₅ and ³P₀ → ³H₅ at 506, 536 and 548 nm was dominant.

• Journal of the Korean Vacuum Society
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• v.20 no.1
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• pp.35-41
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• 2011

In this study, the interface soaking effect in InAs/GaAs strained-layer superlattice (SLS) on crystalline phase modulation has been analyzed by the x-ray diffraction (XRD) curve. The strain variation induced by As and/or Sb soaking was determined by the separation angle between the substrate peak and the 0th-order superlattice satellite peak in the XRD spectra. Contrated that the As/InAs soaking arises minor GaAs-like interfacial layer, the Sb/GaSb soaking induces InSb-like one. The Fourier-transformed curves of the Pendellosung interference oscillation shows that the optimum soaking times of As/InAs and Sb/GaSb are 2 sec and 12 sec, at which the highest crystallineity has, respectively. An anomalous twin-peak phenomenon that a satellite peak splits into two peaks was observed in the SLS structure co-soaked by As and Sb at InAs${\rightarrow}$GaSb interfaces. We suggest that it may be resulted from coexistence of two kinds crystalline phases of InAsSb and GaAsSb due to intermixing of In${\leftrightarrow}$Ga and Sb${\leftrightarrow}$As.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.24 no.4
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• pp.135-139
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• 2014

The hydride vapor phase epitaxy (HVPE) grown GaN samples to precisely measure the surface characteristics was applied to a molten KOH/NaOH wet chemical etching. The etching rate by molten KOH/NaOH wet chemical etching method was slower than that by conventional etching methods, such as phosphoric and sulfuric acid etching, which may be due to the formation of insoluble coating layer. Therefore, the molten KOH/NaOH wet chemical etching is a better efficient method for the evaluation of etch pits density. The grown GaN single crystals were characterized by using X-ray diffraction (XRD) and X-ray rocking curve (XRC). The etching characteristics and surface morphologies were studied by scanning electron microscopy (SEM). From etching results, the optimum etching condition that the etch pits were well independently separated in space and clearly showed their shape, was $410^{\circ}C$ and 25 min. The etch pits density obtained by molten KOH/NaOH wet chemical etching under optimum etching condition was around $2.45{\times}10^6cm^{-2}$, which is commercially an available materials.

• Journal of the Korean Vacuum Society
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• v.22 no.6
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• pp.306-312
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• 2013

Single-crystalline InSb nanowire was synthesized on $SiO_2$ wafer via vapor-liquid-solid (VLS) mechanism using chemical vapor deposition method. According to the source container system (open or close) which contain InSb powder and $SiO_2$ wafer, the single-crystalline InSb nanowires have different growth mechanisms. Structural characterization of the InSb nanowires was examined by scanning electron microscope (SEM). Composition of the nanowires was investigated using x-ray diffraction (XRD) and energy dispersive x-ray spectroscopy (EDS). This study demonstrates that length and diameter of the InSb nanowires are long and thick using open-boat system by VLS and additional vapor-solid (VS) mechanisms, because open-boat system can carry a large amount of vapor-phase InSb precursor than close-boat system.