• Journal of Magnetics
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• v.7 no.1
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• pp.18-20
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• 2002

The charge structures of (LSMO) and of the combined system $(La_{ 0.6}Sr_{0.4}FeO_3$(LSMO) and of the combined system (La_{0.6}Sr_{0.4}MnO_3)_{0.7}(La_{0.6}Sr_{0.4}/FeO_3)_{0.3}$are investigated by using M$\ddot{o}$ssbauer spectroscopy. The antiferromagnetically ordered $(La_{0.6}Sr_{0.4}FeO_3$(LSFO) has possible charges of Fe^{3+} and Fe^{4+}$, which include a low-spin $Fe^{4+}$ state at and above 230 K. The temperature dependences of the M$\ddot{o}$ssbauer spectra for the $(La_{ 0.6}Sr_{0.4}FeO_3$ system and for the combined $(LSMO)_{ 0.7}(LSFO)_{0.3}$ system are fitted as three sets of Zeeman patterns corresponding to $Fe^{3+}$ and $Fe^{4+} below 230 K. At and above 230 K, the fitted M$\ddot{o}$ssbauer spectra for the combined system are the same in all temperature ranges. Above 230 K, $(La_{0.6}Sr_{0.4}FeO_3$ spectrum consists of two sets of six Lorentzians for $Fe^{3+}$ and one line for low spin $Fe^{4+}$. It is worth noting that large fields are induced in the combined system.

• Resources Recycling
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• v.2 no.2
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• pp.9-15
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• 1993

In this study, magnetite($Fe_3$$O_4$) from the converter dust of the Kwangyang steel making factory has been recove-red by means of the magnetic separation and the sedimentation column. The magnetite recovered from the dust is used for the preparation of Sr-ferrite instead of hematite. The results obtained in this study as follows : 1. The converter EP dust of the Kwangyang steel making factory are composed of $\alpha$-Fe, ($Fe_3$$O_4$) wustite etc. Magnetite in the converter EP dust is recovered by using sedimentation column and plastic bonding magnet. 2. It was confirmed that Sr-ferrite synthesis could be possible without oxidizing roasting of the magnetite. The steps of Sr-ferrite formation are proposed as follows : I$SrCO_3$ $+Fe_3$O$_4$+1/2(1-X)$O_2$longrightarrow$\alpha$ $-Fe _2$$O_3$ $+SrFeO _3$\ulcorner+$CO_2$II. $5.5\alpha$ $-Fe_2$$O_3$ $+SrFeO_3$\ulcornerlongrightarrowSrFe\ulcornerO\ulcorner+1/2(1/2-X)$O_2$3. By using magnetite from the dust insted of hematite, the hard Sr-ferrite magnet of (B.H)\ulcorner=2.64MGOe in the magnetic characteristics was succesfully prepared.

• Journal of the Korean Ceramic Society
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• v.40 no.2
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• pp.191-197
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• 2003

Sr ferrites with various compositions were applied to the decomposition of $CO_2$ to mitigate the greenhouse effect. In the reduction reaction of Sr ferrites up to 80$0^{\circ}C$, starting temperature was lower with increasing of Sr content in Sr ferrite. However, the reactivity was higher with decreasing Sr content. In the $CO_2$ decomposition reaction with reduced Sr ferrites, the amount of CO and C were depended on the ratio of Sr and Fe in Sr ferrite. With increasing Sr content. larger amount of C were deposited on the surface of ferrite. Therefore, in order to apply Sr ferrites for the decomposition of $CO_2$, it is necessary to control the ratio of Sr and Fe according to the conditions used.

• Advances in materials Research
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• v.1 no.2
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• pp.161-168
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• 2012

Nanoflake composite multi core-shell $SrFe_{12}O_{19}/Fe_3O_4$/PEG/Polypyrrole was synthesized by in situ polymerization method. In this paper, the fabrication of $SrFe_{12}O_{19}$ nanoflake is as first core by solgel method. Then fabricated a shell layer from magnetic nanoparticles of $Fe_3O_4$, which synthesized by coprecipitation technique, onto the $SrFe_{12}O_{19}$ nanoflake. Polyethylene glycol (PEG) as a polymer layer and as second shell was coated onto the before core-shell. Than core-shell $SrFe_{12}O_{19}/Fe_3O_4$/PEG was used as template for the preparation of $SrFe_{12}O_{19}/Fe_3O_4$/PEG/Polypyrrole composite. Final composite has a conductive property among $4.23{\times}10^{-2}Scm^{-1}$ and magnetic property about $M_s$=2.99 emu/g. Also final composite in soluble at organic solvent such as DMF and DMSO and has a flake structure. Conductivity and magnetic property respectively determine by four-probe instrument and vibrant sample magnetometer (VSM), morphology and article size determined by FE-SEM, TEM and XRD.

• Progress in Superconductivity and Cryogenics
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• v.20 no.1
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• pp.28-31
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• 2018

Phase diagrams of electron- and hole-doped $Sr_2VO_3FeAs$ are investigated using Co and Mn substitution at Fe site. Metallic nature survives only for Co (electron) doping, not for Mn (hole) doping. The conductivity of $Sr_2VO_3(Fe,M)As$ (M=Mn,Co) is sensitive to the structural modification of FeAs microstructure rather than carrier doping. This finding implies that the FeAs layer plays a dominant role on the charge conduction, thus the $SrVO_3$ layers should be considered as an insulating block. Also, we found that the superconductivity is rapidly suppressed by both dopants. This result is different from the conventional behavior that superconductivity is induced by doping in the most of Fe pnictides. Our finding strongly supports the uniqueness of $Sr_2VO_3FeAs$ among the Fe pnictide superconductors.

• Journal of Sensor Science and Technology
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• v.17 no.3
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• pp.203-209
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• 2008

Thick film formaldehyde (HCHO) gas sensors were fabricated by using $La_1_{-x}Sr_xMO_3$ (M= Fe, Co, Mn) ceramics. The powders of $La_1_{-x}Sr_xMO_3$ (M=Fe, Co, Mn) were synthesized by conventional solid-state reaction method. By using the $La_1_{-x}Sr_xMO_3$ (M=Fe, Co, Mn) paste, the thick-film formaldehyde sensors were prepared on the alumina substrate by silkscreen printing method. The experimental results revealed that $La_1_{-x}Sr_xMO_3$ (M= Fe, Co, Mn) ceramic powder has a perovskite structure and the thick-film sensor shows excellent gas-sensing characteristics to formaldehyde gas (sensitivity of $La_{0.8}Sr_{0.2}FeO_3$, S= 14.7 at operating temperature of $150^{\circ}C$ in 50 ppm HCHO ambient).

• Journal of the Korean Ceramic Society
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• v.34 no.5
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• pp.453-460
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• 1997

Sr-ferrite having magnetoplumbite structure is similar to Ba-ferrite in magnetic characteristics, but better magnetic characteristics for using motor application. To improve remanence magnetic flux density(Br) and coercive force(iHc), it is necessary that sintered ferrites must have high density and grain size less than 1 $\mu$m. By varying n values in SrO.nFe2O3 basic composition, calcination temperature, and BaO addition, Sr-ferrite powder and sintered specimen was prepared. The n values, calcination temperature, and BaO addition affected secondary phase formation, particle size, and particle shape. BaO addition enhanced Fe2O3 secondary phase and hexagonal shape particle. Fe2O3 phase reduced sintered density which greatly decreased Br.

• Journal of the Korean Magnetics Society
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• v.8 no.2
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• pp.67-73
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• 1998

Crystallographic and magnetic properties of perovskite $Gd_{1-x}Sr_xFeO_{3-y}$ (x=0.0, 0.5) substituted $Sr^{2+}$ having larger inoic radius than $Gd^{3+}$ at GdFeO$_3$have been studied by x-ary diffraction, M$\ "{o}$ssbauer spectroscopy, and VSM. The cystal structures are found to be orthorhombic with the lattice parameters : $a_o=5.53\;{\AA},\;b_o=5.608\;{AA},\;C_o=7.724\;{\AA}$ for $Gd_{0.5}Sr_{0.5}FeO_{3-y}$ (x=0.0, 0.5) have been investigated over temperature range from 4.2 to 690 K using the M$\ "{o}$ssbauer technique. The Neel temperatuer of $Gd_{1-x}Sr_xFeO_{3-y}$ system is 690 K with x value of 0.0 and 515 K with x value of 0.5. Analysis of M$\ "{o}$ssbauer spectra Mohr's salt analysis for $Gd_{1-x}Sr_xFeO_{3-y}$ demonstrated the existence of the mixed valence states of iron and the coordination state of $Fe^{3+}$ and $Fe^{4+}$ ions. The Corresponding hyperfine parameters for GdFeO$_3$ are compatible with S=5/2 $Fe^{3+}$ in octahedral cooedination.l cooedination.

• Membrane Journal
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• v.22 no.1
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• pp.8-15
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• 2012

Tubular $Ba_{0.5}Sr_{0.5}Co_{0.8}Fe_{0.2}O_{3-{\delta}}$ membranes with $La_{0.6}Sr_{0.4}Ti_{0.3}Fe_{0.7}O_{3-{\delta}}$ porous coating layer were prepared by extrusion and dip coating technique. XRD and SEM result showed the tubular membrane possessed the perovskite structure and porouscoating layer (thickness= about $2{\mu}m$) in surface. The oxygen permeation test was measured at condition of ambient air (feed side) and vacuum (permeate side) in the temperature range from 750 to $950^{\circ}C$. The oxygen permeation flux of $Ba_{0.5}Sr_{0.5}Co_{0.8}Fe_{0.2}O_{3-{\delta}}$ tubular membrane with $La_{0.6}Sr_{0.4}Ti_{0.3}Fe_{0.7}O_{3-{\delta}}$ porous coating layer reached maximum $3.2mL/min{\cdot}cm^2$ at $950^{\circ}C$ and was higher than non-coated $Ba_{0.5}Sr_{0.5}Co_{0.8}Fe_{0.2}O_{3-{\delta}}$ tubular membrane. Long-term stability test result indicated that the oxygen permeation flux was quite stable during the 11 day.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.29A no.4
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• pp.22-27
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• 1992

The cyclic voltammogram characteristics at the magnetized SrO${\cdot}6Fe_{2}O_{3}$ ceramics/(($10^{-3}$M KCI + p-Si powders) and /(($10^{-4}$M CsNO$_3$ + n-GaAs powders) suspension interfaces have been studied using the microelectrophoresis and the cyclic voltammetric method. The negatively charged ions are specifically absorbed on the virgin and the magnetized SrO${\cdot}6Fe_{2}O_{3}$ ceramics surfaces. The zeta potentials of the p-Si and n-GaAs colloidal semiconductors are + 41mV and -44.8mV, respectively. The magnetization effects act as potential barriers at the magnetized SrO${\cdot}6Fe_{2}O_{3}$ interfaces. The positivelely charged p-Si and the negatively charged n-GaAs colloidal semiconductors act as potential barriers at the virgin SrO${\cdot}6Fe_{2}O_{3}$ interfaces. On the other hand, the charged p-Si and n-GaAs colloidal semiconductors act as potential barrier scavengers at the magnetized SrO${\cdot}6Fe_{2}O_{3}$ interfaces. The magnetization effects and the charged colloidal semiconductor effects are irreversible and interdependent.