• Journal of the Korean Ceramic Society
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• v.39 no.10
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• pp.994-1000
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• 2002

Oxygen permeability and the mechanical properties of mixed ionic-electronic conductive $La_{0.6}Sr_{0.4}Co_{0.2}Fe_{0.8}O_{3-{\delta}}$ perovskite-type membrane, fabricated by solid state reaction, were investigated with regard to microstructure. The microstructure of the membrane was controlled by changing the sintering temperature and holding time. The average grain size and relative density were evaluated as a function of sintering conditions. As the fraction of grain boundary decreased, oxygen permeability showed a tendency to increase. Especially the maximum oxygen flux of 0.37 ml/$cm^2$${\cdot}$min was measured for the specimen sintered at 1300${\circ}C$ for 10 h, which has high density and relatively large grain size. Fracture strength was dependent on the relative density of sintered body, while fracture toughness increased with average grain size.

• Bulletin of the Korean Chemical Society
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• v.17 no.4
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• pp.321-324
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• 1996

Sr1+xSm1-xFeO4-y solid solutions with a composition range 0.00 ≤x≤1.00 have been prepared at 1200 ℃ in air under normal atmospheric pressure. All the solutions exhibit the K2NiF4-type structure of tetragonal system. Mohr salt analysis shows that the mole ratio of Fe4+ ion to Fe3+ ion or the τ value increases with the x value. Nonstoichiometric chemical formulas have been formulated from the x, τ, and y values. Electrical conductivity was measured in the temperature range of 173-373 K under atmospheric air pressure. The conductivities of each sample are varied within the semiconductivity range. The conductivity at constant temperature increases steadily with x value and activation energies are varied from 0.14 to 0.32 eV. The conduction mechanism of the ferrite system may be proposed as a hopping model of conduction electrons between the mixed valence states. The Mossbauer spectrum for the composition of x=0.00 shows a six line pattern by which the existence of Fe3+(I.S.=0.32 mm/sec) can only be identified. The spectra for the compositions of x=0.50 and 1.00 presents broad single line patterns showing a mixed valence state.

• Journal of the Korean Electrochemical Society
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• v.10 no.1
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• pp.7-13
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• 2007

We synthesized and investigated $La_{0.75}Sr_{0.25}FeO_3$ by Glycine Nitrate Process(GNP) method used as cathode materials for SOFC(solid oxide fuel cell). Optimized amount of glycine is 3.17 mol. ICP elemental composition analysis indicated that the stoichiometry of the synthesized powders have nearly nominal values. SEM images and XRD patterns reveal that the synthesized powder has uniform size distribution and high degree of crystallinity. The sample powders were isostatically pressed to form a pellet. The green body was sintered at $1200^{\circ}C$ and the relative density of the sintered specimens were measured by Archimedes mettled. We measured electrochemical performance of LSF by AC impedance spectroscopy. Resistance of LSF shows lower value than that of LSM throughout all temperature region. The anode-supported solid oxide fuel cell showed a performance of $342mW/cm^2(0.7V,\;488mA/cm^2)$ at $750^{\circ}C$. The electrochemical characteristics of the single cell were examined by at impedance method.

• Korean Journal of Organic Agriculture
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• v.20 no.3
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• pp.385-397
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• 2012

A pot experiment was carried out to examined the effect of electrolyzed micronutrients (Fe, Mn, Zn, Sr, Se, Sn, Co, Ti, and V) solution treatments with nutrient solution and SCB slurry on the mineral content and growth of tomato in cherry tomato (Lycopersicon esculentum). The treatment of nutrient solution (NS)+micronutrients solution (MS) significantly increased the concentrations of Li, Zn, Sr, Se, Ti as compared with that of NS alone in the cherry tomato fruits, and SCB+MS solution treatment significantly increased Li, Zn, Se, Co, Sr, and Ti contents as compared with SCB treatment. The micronutrient contents of MN+SCB+MS treatment were significantly higher in Li, Zn, Se, Co and in Ti than those of SCB and NS treatment, respectively. The growth and yield of cherry tomato fruits was highest with NS treatment. The yield indices of cherry tomato treated with NS+MS treatment and SCB+NS+MS were 97% and 94% of NS treatment. In conclusion, it seems to be possible to produce micronutrient-fortified cherry tomato by the mixed treatment of electrolyzed micronutrients.

• Proceedings of the Korean Magnestics Society Conference
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• 2002.12a
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• pp.86-87
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• 2002

Fe과 Mo이 교대로 정렬해 있는 이중 페로브스카이트 구조를 갖는 $A_{2-x}$FeMo $O_{6}$(A=Ca, Sr, Ba) 화합물들은 망간 산화물들에 비해 높은 $T_{c}$ (310-420K)의 준강자성 상태를 갖는다.$^{1.3}$ 이 화합물들은 F $e^{3+}$ (S=5/2) 와 M $o^{5+}$(S=1/2) 스핀들 사이의 커다란 반강자성 상호작용으로 이론적으로 4$\mu$$_{B}$/f.u.의 $M_{s}$ 값을 갖는다. A-site의 평균 이온 반경( $r_{A}$)이 증가함에 따라 이 화합물들의 결정구조는 Monoclinic(A=Ca)에서 Tetragonal(Sr)과 Cubic(Ba)으로 점진적으로 변화한다.$^3$(중략)(중략)략)략)

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.11a
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• pp.217-220
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• 1999

We investigated the effects of doping elements on the Bi-Sr-Ca-Cu-0 ceramics. The doping elements can be classified into groups depending on their supeconducting characteristics in the Bi -Sr-Ca-Cu -O structure. The first group of doping elements(Co, Fe, Ni and Zn) substitute into the copper site and can reduce the critical temperatures of the 2223 and 2212 phases. The second group of doping elements(Y and La) substitute into the Ca site and cause the disappearance of the 2223 phase and increase the critical temperatures in the 2212 phase.

• Ocean and Polar Research
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• v.26 no.2
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• pp.231-243
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• 2004

Sequential extraction was carried out on twenty two subsamples of three ferromanganese crusts from three seamounts (Lemkein, Lomilik, and Litakpooki) near the Marshall Islands in the western Pacific. The extraction was designed to fractionate Fe-Mn crust forming elements into low defined groups: (1) exchangeable and carbornate, (2) Mn-oxide, (3) Fe-oxyhyd.oxide, and (4) residual fraction. X-ray diffraction result shows that target material were well removed by each extraction step except for CFA in phosphatized crusts generation. According to chemical analysis of each leachate, most of elements in the Fe-Mn crusts are bound with two major phases. Mn, Ba, Co, Ni, Zn, (Fe, Sr, Cu, and V) are strongly bounded with Mn-oxide $({\delta}-MnO_2)$ phase, whereas Fe, Ti, Zr, Mo, Pb, Al, Cu,(V, P, and Zn) show chemical affinity with Fe-oxyhydroxide phase. This result indicates that significant amount of Al, Ti, and Zr can not be explained by detrital origin. Ca, Mg, K, and Sr mainly occur as exchangeable elements and/or carbonate phase. Outermost layer 1 and inner layer 2 which are both young crusts generations are similar in chemical speciations of elements. However, some of Fe-oxyhydroxide bounded elements (Pb, Y, Mo, Ba, Al, and V) in phosphatized innermost layer 3 are released during phosphatization and incorporated into phosphate (Pb, Y, Mo, and Ba) or Mn-oxide phase (Al and V). Our sequential extraction results reveal that chemical speciations of elements in the hydrogenetic crusts are more or less different from interelemental relationship calculated by statistical method based on bulk chemistry.

• The Korean Journal of Quaternary Research
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• v.7 no.1
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• pp.69-91
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• 1993

A total of 76 surface sediment samples, collected from the Korean west coast and the eastern Yellow Sea areas, were analyzed for their elemental composition in order to understand the geochemical characteristics of these deposits. The analyzed elements included 9 major elements (Al, Fe, Na, K, Mg, Ca, Ti, P, Mn), 8 minor elements (Sr, Ba, V, Cr, Co, Ni, Cu, Zn), organic carbon and calcium carbonate. Contents of most analyzed elements, excluding K and Ba, were generally low compared to those of average crust. Contents of most elements, except K and Ca, also correlated with sediment grain size, though the degree of relationship varied widely from one element to another. For fine-grained sediments, a distinction could be made between those in the central Yellow Sea and those in the Keum Estuary based on their characteristic elemental composition: the former were rich in Fe, Na, K, Mg, Ca and V, and the latter in Mn, Co and Ni. The element/aluminium ratios, on the other hand, showed that the central Yellow Sea muds were enriched in Fe, Mg, V, Ni, Cu and Zn and depleted in K, Mn, Ba and Sr relative to the mud located near the Korean Peninsula. Based on the analysis of these results, as well as of the influences of particular mineral phases or pollution effects, we could suggest geochemical criteria which can be used in distinguishing muds from the two different sources, the Keum River and the Yellow River: the former by the higher Mn content and the latter by the higher Mg and V contents, relative to each other.

• Proceedings of the Korean Magnestics Society Conference
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• 2017.05a
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• pp.216-216
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• 2017

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.21 no.5
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• pp.214-217
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• 2011

A fresnoite glass-ceramics has been investigating considerably because of the second order nonlinearity as well as its permanent optical nonlinearity. However, the chemical compositions of transparent glass-ceramics examined in the previous studies have been limited to adjust the composition close to fresnoite stoichiometrically. In this study, to investigate the effect of strontium ions in glass-ceramics on second order nonlinearity, $K_2O-TiO_2-SiO_2$ (KTS) glasses soaked in molten $Sr(NO_3)_2$ were prepared. Crystalline phases of the soaked glasses were measured by X-ray diffraction (XRD) as soaking times and additional heat treatment. The exchange of strontium ions into the glass was verified by Field Emission Scanning Electron Microscope (FE-SEM). And the phenomena of second order harmonic generation (SHG) was observed using Nd-YAG laser.