• Journal of the Korean Chemical Society
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• v.35 no.6
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• pp.617-624
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• 1991

Nonstoichiometric solid solutions of $Y_{1-x}A_xFeO_{3-y}$ (A = Ca, Sr) systems with perovskite structure were prepared for x = 0.00, 0.25, 0.50, 0.75 and 1.00 at 1200$^{\circ}C$ under atmospheric pressure, respectively. Crystallographic structures of the solid solutions of all compositions have been determined by the analysis of X-ray diffraction patterns. Reduced lattice volume of the $Y_{1-x}Ca_xFeO_{3-y}$ system was decreased with increasing x value and that of the $Y_{1-x}Sr_xFeO_{3-y}$ system was increased with increasing the x value. The mole ratios of $ Fe^{4+}$ to $ Fe^{3+}$, ${\tau}$, values in the solid solutions have been determined by Mohr salt's method of analysis and then the mixed valency was identified by Mossbauer spectroscopic analysis at 298 K. The y values were calculated from the x and ${\tau}$, and then nonstoichiometric chemical formulas were fixed. The conduction mechanism could be explained by hopping model of the conduction electrons between the mixed valence states.

• Korean Journal of Food Science and Technology
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• v.52 no.1
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• pp.31-39
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• 2020

The effects of heat-moisture treatment (HMT) on the functional properties of high amylose rice starches (HARSes) purified from Korean rice varieties (A-type Goami and Singil and B-type Dodamssal and Goami2) were investigated. HMT was accomplished with moisture contents of 18 and 27% and heated at 100℃ for 16 h. While the amylose content, swelling power and solubility decreased after HMT, the water binding capacity and resistant starch (RS) content increased with increasing moisture content after HMT. The X-ray diffraction patterns of all HARSes did not change after HMT, but a decrease in the intensity of peak at 2θ=5° was observed in B-type HMT HARSes. While the starch granules aggregated after HMT, their shape and size remained unchanged. B-type HARSes exhibited higher gelatinization temperatures and lower pasting viscosities than A-type HARSes following HMT. The results, thus, suggest that while the crystalline intensity of B-type Dodamssal and Goami2 rice starches did not change after HMT, the RS content, water binding capacity, and pasting temperatures of all HARSes increased with increasing moisture content after HMT.

• Applied Microscopy
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• v.34 no.4
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• pp.255-264
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• 2004

The three-dimensional (3D) structure of an inorganic crystal, $SmZn_{0.67}Sb_2$ (space group P4/nmm, $a=4.26{\AA}\;and\;c=10.37{\AA}$) was solved by electron crystallography. High resolution electron microscopy (HREM) images from 3 different major zone axes and selected-area electron diffraction patterns from 16 different zone axes were combined to obtain a 3D information. A crystallographic image processing (CIP) of HREM images was used for more accurate determination of the crystal structure. As a result of this electron crystallography, average phase errors (${\Phi}_{res}$) of [001], [100] and [110] HREM images are $17.0^{\circ},\;8.3^{\circ}\;and\;21.9^{\circ}$, respectively. Xray crystallography of $SmZn_{0.67}Sb_2$ has attempted to compare accuracy of the structure determination by electron crystallography, which resulted in the cell parameters of $a=4.2976(6){\AA}\;and\;c=10.287(2){\AA}$, and the R-factor ($R_{sym}$) of 4.16%.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.10 no.3
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• pp.199-204
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• 2000

In this study, the ZnS nanosized thin films that could be used for fabrication of blue light-emitting diodes, electro-optic modulators, and n-window layers of solar cells were grown by the solution growth technique (SGT), and their structural and optical properties were examined. Based on these results, the quantum size effects of ZnS were systematically investigated. Governing factors related to the growth condition were the concentration of precursor solution, growth temperature, concentration of aq. ammonia, and growth duration. X-ray diffraction patterns showed that the ZnS thin film obtained in this study had the cubic structure ($\beta$-ZnS). When the growth temperature was $75^{\circ}C$, the surface morphology and the grain size uniformity were the best. The energy band gaps of samples were determined from the optical transmittance valued, and were shown to vary from 3.69 eV to 3.91 eV. These values were substantially higher than 3.65 eV of bulk ZnS, demonstrating that the quantum size effect of SGT grown ZnS is remarkable. Photoluminescence (PL) peaks were observed at the positions corresponding to the lower energy than that to energy band gap, illustrating that the surface states were induced by the ultra-fineness of grains in ZnS films. Particularly, for the first time, it is reported for the SGT grown ZnS that the PL peaks were shifted depending on the grain size.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.173-173
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• 2010

$Bi_4Ti_3O_{12}$ ($B_4T_3$) is a unique ferroelectric material that has a relatively high dielectric constant, high Curie temperature, high breakdown strength, and large spontaneous polarization. As a result this material has been widely studied for many applications, including nonvolatile ferroelectric random memories, microelectronic mechanical systems, and nonlinear-optical devices. Several reports have appeared on the use of Mn dopants to improve the electrical properties of $B_4T_3$ thin films. Mn ions have frequently been used for this purpose in thin films and multilayer capacitors in situations where intrinsic oxygen vacancies are the major defects. However, no systematic study of the optical properties of $B_4T_3$ films has appeared to date. Here, we report optical data for these films, determined by spectroscopic ellipsometry (SE). We also report the effects of thermal annealing and Mn doping on the optical properties. The SE data were analyzed using a multilayer model that is consistent with the original sample structure, specifically surface roughness/$B_4T_3$ film/Pt/Ti/$SiO_2$/c-Si). The data are well described by the Tauc-Lorentz dispersion function, which can therefore be used to model the optical properties of these materials. Parameters for reconstructing the dielectric functions of these films are also reported. The SE data show that thermal annealing crystallizes $B_4T_3$ films, as confirmed by the appearance of $B_4T_3$ peaks in X-ray diffraction patterns. The bandgap of $B_4T_3$ red-shifts with increasing Mn concentration. We interpret this as evidence of the existence deep levels generated by the Mn transition-metal d states. These results will be useful in a number of contexts, including more detailed studies of the optical properties of these materials for engineering high-speed devices.

• Journal of the Korean Society of Food Science and Nutrition
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• v.32 no.7
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• pp.953-959
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• 2003

This study examined physicochemical properties of two waxy rice starches, shinsun and black rice starches. Proximate compositions of both samples were similar. The major minerals in the shinsun rice starches were Ca, Mg, P and Na, whereas those in black rice starches were Ca, P, Fe and Mg. The major particle size of shinsun rice starch was 6.97 micron and that of black rice starch was 6.27 micron. In iodine reaction, maximum absorbance wavelength (λmax) and absorbance at 625nm of black rice starch were higher than those of shinsun rice starch. Intrinsic viscosity of black rice starch (183mL/g) was higher than that of shinsun rice starch (178 mL/g). Water binding capacity was similar in both samples. Swelling power and solubility of black rice starch were lower than those of shinsun rice starch. X-ray diffraction patterns of all samples showed traditional A type of cereals as shown peaks at 15.2 (15.0), 17.2 (17.15), 18.05 (17.95), 23.25 (23.15)$^{\circ}$. The common shape of SEM was observed in both waxy rice starches.

• Journal of the Korean Electrochemical Society
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• v.14 no.3
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• pp.184-190
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• 2011

$LiMn_2O_4$ with mesoporous hollow sphere shape was synthesized by precipitation method with silica template. The synthesized $LiMn_2O_4$ has nanosized first particle and mesoporous hollow sphere shape. Silica template was removed by chemical etching method using NaOH solution. When the concentration of NaOH solution was increased, first particle size of manganese oxide was decrease and confirmed mesoporous hollow shpere shape. X-ray diffraction(XRD) patterns revealed that the synthesized samples has spinel structure with Fd3m space group. In case the ratio of silica and maganese salt increased, the size of first particles was decreased. The tetragoanal $LiMn_2O_4$ with micron size was synthesized at ratio of silica and manganese salt over 1 : 9. The prepared samples were assembled as cathode materials of Li-ion battery with 2032 type coin cell and their electrochemical properties are examined by charge-discharge and cyclic performance. Electrochemical measurements show that the nano-size particles had lower capacity than micron-size particles. But, cyclic performance of nano-size particles had better than that of micron-size particles.

• Korean Journal of Food Science and Technology
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• v.40 no.3
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• pp.290-296
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• 2008

This study examined the physicochemical properties of chemically and enzymatically cross-modified waxy rice starches. The waxy rice starch was cross-linked using phosphorous oxychloride, and then partially hydrolyzed with four commercial ${\alpha}$-amylases (Fungamyl, Termamyl, Liquozyme, Kleistase). Swelling power and the moisture sorption isotherm did not change with cross-modification. Two cross-modified waxy rice starches (hydrolyzed with Termamyl and Liquozyme) showed higher solubilities than native starch and the two other cross-modified starches (hydrolyzed with Fungamyl and Kleistase). In terms of RVA characteristics, the two cross-modified waxy rice starches hydrolyzed with Termamyl and Liquozyme, respectively, had lower peak viscosity, holding strength, and final viscosity than the native starch. However, the two starches hydrolyzed with Fungamyl and Kleistase, respectively, revealed higher peak viscosity, holding strength, and final viscosity than the native starch. No differences were displayed in the X-ray diffraction patterns and DSC thermal characteristics of the cross-modified waxy rice starch as compared to both the native and cross-linked starches, indicating that cross-linking and enzymatic hydrolysis occurred in the amorphous region and did not alter the crystalline region.

• Korean Journal of Food Science and Technology
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• v.31 no.3
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• pp.612-618
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• 1999

Physicochemical properties of amaranth starch were compared with those of waxy rice and waxy corn starches. Amaranth starch granules vary from $1.1{\sim}1.9\;{\mu}m$ in diameter and are polygonal in shape. Total amylose contents from waxy rice, waxy corn and amaranth starches were 0.01, 0.03 and 0.07%, respectively. Swelling power of amaranth starch granule was slightly different from waxy rice. The swelling power of amaranth increased at $70^{\circ}C$. X-ray diffraction patterns of amaranth and other waxy cereal starches showed an A-type crystalline structure. Relative crystallinities of their starches were similar. According to pasting properties by Rapid Visco-Analyzer, amaranth starch showed a very high gelatinization temperature $(75.1^{\circ}C)$ and lower viscosity and higher stability than other waxy cereal starches during heating and cooling cycle. Peak onset temperatures (To) of starches from waxy rice, waxy corn and amaranth in DSC thermograms were $58.7{\sim}64.0$, 67.2 and $71.5^{\circ}C$, respectively, and their peak enthalpies were similar. Enthalpy of reheated amaranth starch after 3 day storage at $4^{\circ}C$ was higher than those of waxy corn and rices starchs.

• Journal of the Korean Vacuum Society
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• v.22 no.2
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• pp.79-85
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• 2013

Rare earth ions, either $Eu^{3+}$ or $Dy^{3+}$-doped $CaMoO_4$ phosphors were synthesized by using the solid-state reaction method. The crystalline structure of all the phosphor powders, irrespective of the type and concentration of activator ions, was found to be a tetragonal system with the main diffraction peak at (112) plane. For $Eu^{3+}$-doped $CaMoO_4$ phosphors, the grain particles showed an increasing tendency and the pebble-like patterns with a very homogeneous size distribution in the range of 0.01~0.10 mol of $Eu^{3+}$ ions concentration, and the excitation spectra were composed of a broad band centered at 311 nm and weak multiline peaked in the range of 360~470 nm. The dominant emission spectrum was the strong red emission centered at 618 nm due to the $^5D_0{\rightarrow}^7F_2$ transition of $Eu^{3+}$ ions. For $Dy^{3+}$-doped $CaMoO_4$ powders, excitation spectra showed a charge transfer band centered at 303 nm and relatively weak bands resulting from the transitions of $Dy^{3+}$ ions and the main yellow emission spectrum was observed at 578 nm, which was assigned to the $^4F_{9/2}{\rightarrow}^7H_{13/2}$ transition of $Dy^{3+}$ ions.