• Journal of the Korean Magnetics Society
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• v.16 no.1
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• pp.28-33
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• 2006

La substituted perovskite $BiFeO_3$ have been prepared by a sol-gel method. Magnetic and structural properties of the powders were characterized with Mossbauer spectroscopy, XRD, SEM, and TG-DTA. The crystal structure is found to be a rhombohedrally distorted perovskite structure with the lattice constant $\alpha=3.985{\AA}\;and\;\alpha=89.5^{\circ}.\;Bi_{2/3}La_{1/3}FeO_3$ powders that were annealed at and above $600^{\circ}C$ have a single-phase perovskite structure. However, powders annealed at $900^{\circ}C$ have a typical perovskite structure with small amount of $Bi_2O_3$ phase. The Neel temperature of $Bi_{2/3}La_{1/3}FeO_3$ is found to be $680\pm3K$. The isomer shift value at room temperature is found to be 0.27 mm/s relative to the Fe metal, which is consistent with high-spin $Fe^{3+}$ charge states. Debye temperature far$Bi_{2/3}La_{1/3}FeO_3$ is found to be $305\pm5K$. The average hyperfine field $H_{hf}(T)$ of the $Bi_{2/3}La_{1/3}FeO_3$, shows a temperature dependence of $[H_{hf}(T)-H_{hf}(0)]/H_{hf}(0)=-0.42(T/T_N)^{3/2}-0.13(T/T_N)^{5/2}$ for $T/T_N<0.7$ indicative of spin-wave excitation.

• Bulletin of the Korean Chemical Society
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• v.9 no.5
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• pp.283-288
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• 1988

The titled properties on reduction of the perovskite $LaBO_3$ (B = Fe, Co, Ni) have been investigated by means of temperature-programmed reduction, isothermal reduction and X-ray diffraction methods. Nominal composition of $LaFeO_{3.18},\;LaCoO_{3.00}\;and\;LaNiO_{2.92}$ are determined. Reduction reaction of these mixed oxides differed according to B-site transition metal and thermal stability on reduction decreased as following order: $LaFeO_{3.18}$ > $LaCoO_{3.00}$ > $LaNiO_{2.92}$. From the results of isothermal reaction, kinetics on reduction of the perovskite has been discussed in detail.

• Journal of the Korean Society of Safety
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• v.3 no.1
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• pp.7-13
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• 1988

The oxides in perovskite type, $LaMO_3$ (M=Ni, Cr, Fe, Co), compared with gas sensors which have been used, were synthesised and then examined sensor response comparatively in order to make a thick film gas sensor having a good gas selectivity, durability and simple manufacturing. The oxides in perovskite type, $LaFe_{1-x}O_3$ (x=0.2, 0.4, 0.6, 0.8), which a part of Fe was replaced with Co, were examined with regard to their electric resistance with variable temperature and sensor response for carbon monoxide gas.

• The Journal of Natural Sciences
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• v.15 no.1
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• pp.35-46
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• 2005

$LaFeO_3$ and substituted $LaFeO_3$ mixed oxides were prepared by Citrate and Cyanide method in air $850^{\circ}C$/24h. These oxides of orthorhombic perovskite were characterized by XRD and IR, but substituted $LaFeO_3$ with 0.5mol Cu at B site was not obtained single phase. Also, reduction reaction of un-substituted $LaFeO_3.17$ were two steps but each site substituted oxides were three steps reactions. These means that new reduction step of each site substituted oxides were atributed tot dopant.

• Korean Chemical Engineering Research
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• v.57 no.4
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• pp.584-588
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• 2019

The catalytic combustion of particulate matter (PM) is one of the key technologies to meet emission standards of diesel engine system. Therefore, we herein suggest Ag loaded $La_{0.6}Sr_{0.4}Co_{0.2}Fe_{0.8}O_3$ perovskite web catalyst. They were produced by the electrospinning method. FE-SEM, EDS mapping, XRD, XPS were studied to investigate the crystal and morphological structures of loaded Ag particles and $La_{0.6}Sr_{0.4}Co_{0.2}Fe_{0.8}O_3$ perovskite web catalyst. Following the catalytic soot oxidation, we found that the Ag loaded $La_{0.6}Sr_{0.4}Co_{0.2}Fe_{0.8}O_3$ perovskiteweb catalyst showed the higher catalytic activities (e.g., $T_{50}=490^{\circ}C$) than the only $La_{0.6}Sr_{0.4}Co_{0.2}Fe_{0.8}O_3$ perovskite web catalyst (e.g., $T_{50}=586^{\circ}C$). Thus, this finding suggests that Ag loaded $La_{0.6}Sr_{0.4}Co_{0.2}Fe_{0.8}O_3$ perovskite web catalyst can be a promising candidate for enhancing the soot oxidation.

• Journal of the Korean Chemical Society
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• v.38 no.4
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• pp.276-282
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• 1994

Perovskite-type mixed oxides LaBO$_3$(B = Mn, Fe, Co) were prepared by citrate sol-gel method in $air(850^{\circ}C$, 24h). The oxygen stoichiometries and structures of these oxides were determined by XRD and TPR results as followings; LaMnO$_{3.16}$(a = 5.507, c = 13.329 $\AA$, hexagonal), LaFeO$_{3.17}$(a = 5.554, b = 5.555, c = 7.863 $\AA$, orthorhomibic), LaCoO$_{3.0}$(a = 5.436, c = 13.095 $\AA$, hexagonal). The temperature programmed reduction(TPR) experiments in static 300 torr H$_2$ atmosphere shows that the reduction reaction of LaBO$_3$(B = Mn, Fe, Co) proceeds into two stages, and thermal stabilities of these oxides decreased in the order of LaMnO$_3$ > LaFeO$_3$ > LaCoO$_3$. According to the kinetic analysis the lowest activation energy was obtained for LaCoO$_3$.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.28 no.1
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• pp.44-50
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• 2018

The improved high-performance Fe-based perovskite-type oxides ($La_{0.7}Sr_{0.3}M_xFe_{1-x}O_3$, M = Cu, Cr, Ni) were synthesized by a citrate method and characterized by SEM, EDS, XRD and NMR spectroscopy analyses. The characterization analyses revealed that the stoichiometric amounts of lattice oxygen were existed in all of perovskite samples except for a nickel-doped perovskite. Fe-based perovskites exhibited a surprising result for ortho-para $H_2$ spin conversion reaction, indicating two orders of magnitude higher conversions and conversion rates than commercial $Fe_2O_3$. It was considered that this conversion difference might be attributed to the presence of oxygen vacancies in Fe-based perovskites prepared in this study.

• Korean Chemical Engineering Research
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• v.43 no.6
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• pp.740-744
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• 2005

Perovskite-type oxide $La_{1-x}Sr_xCo_{1-y}Fe_yO_{3-{\delta}}$ sols were prepared by sol-gel method using $La(NO_3)_3{\cdot}xH_2O$, $Sr(NO_3)_2$, $Co(NO_3)_2{\cdot}6H_2O$ and $Fe(NO_3)_3{\cdot}9H_2O$ as starting materials. The properties of the perovskite-type oxide sols were investigated by viscometer, FT-IR, TG-DTA and XRD. The prepared sols showed 1.16 cp in average viscosity, and a strong acidic condition of pH 0.5, irrespective of composition of the starting materials. The viscosity of sols at the same volume decreases, but the gelation time of sols, at which the sol viscosity increases rapidly, increases when increasing La concentration in composition of starting materials.

• Clean Technology
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• v.18 no.3
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• pp.259-264
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• 2012

Perovskite-type oxides were successfully prepared using malic acid method, characterized by TG/DTA, XRD, XPS, TEM and $H_2$-TPR and their catalytic activities for the combustion of benzene were determined. Almost of catalyst showed perovskite crystalline phase and 15-70 nm particle size. The $LaMnO_3$ catalysts showed the highest activity and the conversion reaches almost 100% at $350^{\circ}C$. The catalysts were modified to enhance the activity through substitution of metal into the A or B site of the perovskite oxides. In the $LaMnO_3$-type catalyst, the partial substitution of Sr into site the A-site enhanced the catalytic activity in the benzene combustion. In addition, the partial substitution of Co or Cu into site the B-site also enhanced the catalytic activity and the catalytic activity was in the order of Co > Cu > Fe in the $LaMn_{1-x}B_xO_3$ (B = Co, Fe, Cu) type catalyst.

• Journal of the Korean Chemical Society
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• v.55 no.4
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• pp.697-702
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• 2011

The new layered perovskite manganites $La_{0.5}Sr_{1.5}Mn_{0.5}Cr_{0.5-x}Fe_xO_4$ (x=0.15, 0.3) have been prepared by standard ceramic method. The powder X-ray diffraction studies show that the phases crystallize with tetragonal unit cell in the space group I4/mmm. The electrical transport properties suggest that the phases show insulating behaviour and the electrical conduction in the phases occurs by a 3D variable range hopping mechanism. The magnetic properties suggest that both the phases are antiferromagnetic.