• Journal of the Korean Magnetics Society
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• v.26 no.6
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• pp.185-189
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• 2016

By employing photoemission spectroscopy (PES) and soft X-ray absorption spectroscopy (XAS), the electronic structure of the candidate half-metallic antiferromagnet of $Mn_3Ga$ Heusler compound has been investigated. We have studied two ball-milled $Mn_3Ga$ powder samples, one after annealing and the other without annealing, respectively. Based on the Mn 2p XAS study, we have found that Mn ions are nearly divalent in $Mn_3Ga$ and that the Mn ions having the locally octahedral symmetry and those having the locally tetrahedral symmetry are both present in $Mn_3Ga$. We have found relatively good agreement between the measured valence-band PES spectrum of $Mn_3Ga$ and the calculated density of states, which is in agreement with the half-metallic electronic structure of $Mn_3Ga$.

• Journal of the Korean Magnetics Society
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• v.17 no.1
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• pp.1-5
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• 2007

The 1R(Infra-Red) spectrum and PL(Photoluminescence) of the antiferromagnetic pure $MnF_2$ and the single crystal $MnF_2(1.5%\;EuF_3)$ with the rutile structures were measured. The detailed analysis of the measured PL data showed the differences of the optical property between the single crystal $MnF_2(1.5%\;EuF_3)$ and the pure $MnF_2$. It was found that the additional PL peak by the doping of the $EuF_3$ in $MnF_2$ is originated from the f-d transition of $Eu^{3+}$ from the temperature dependent intensity measurement.

• Journal of the Korean Electrochemical Society
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• v.16 no.3
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• pp.162-168
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• 2013

$Li_2MnO_3-LiMO_2$(M=Ni, Co, Mn) nano-composite is a promising cathode material for xEV application due to its high theoretic capacity. However high voltage operating system of $Li_2MnO_3-LiMO_2$(M=Ni, Co, Mn) has worked as a hurdle in its application because of the inherent demerits, such as cycle life degradation and gas evolution. In order to enhance cell performance of $Li_2MnO_3-LiMO_2$(M=Ni, Co, Mn)/graphite cell, we examined electrolyte mainly composed of FEC, fluroalkyl ether and $LiPF_6$ (F-based EL). F-based EL showed much better discharging retention ratio than 1.3 M $LiPF_6$ EC/EMC/DMC (3/4/3, v/v/v) (STD). Furthermore gas evolution, especially CO and $CO_2$ during $60^{\circ}C$ storage for 30 days was dramatically reduced owing to thermal stable SEI formation effect of F-based EL.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.11 no.4
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• pp.154-159
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• 2001

(Li,Al)$MnO_2(OH)_2$:Co compound was synthesized by hydrothermal method. $MnO_2$, LiOH.$H_2$O, $Co_3O_4$ and $Al(OH)_3$ were used as starting materials and the optimum conditions for synthesis of monolithic (Li,Al)$MnO_2(OH)_2$:Co compound were as follows : reaction temperature; $200^{\circ}C$, reaction time; 3 days, hydrothermal solvent; 3M-KOH solution, reaction apparatus; seesaw type, atomic ratio of Li:Al:Mn;Co = 1:2.1:2.5~2:0.5~1. Monolithic(Li,Al)$MnO_2(HO)_2$:Co compound synthesized in this work had a god crystallinity and excellent color forming effect as a blue pigment compatible with natural mineral. The particles of the synthesized (Li,Al)$MnO_2(OH)_2$:Co compound have hexagonal plate shape with the size of 0.5~1 $\mu\textrm{m}$.

• Journal of the Korean Ceramic Society
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• v.17 no.2
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• pp.80-88
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• 1980

The sintering phenomena and piezoelectric properties of PZT ceramics of composition $Pb(Zr_{0.54} Ti_{0.46})O_3$ were investigated when a small quantity of $La_2O_3$ , $LaMnO_3$, $LaCrO_3$ were added. The unwanted chemical composition change in PZT during sinterin porces du to PbO evaporation poses a severe problem in PZt manufacturinig. It is observed tat an addition of small amount of $LaMnO_3$ to PZT markedly decreases the evaporation of PbO during sintering . The green compact of (1-x) PZT.xLaMnO3(x=0.02~0.10) could be sintered of under O2 atmosphere alone with no significant loss of PbO. The planar coupling factor kp of the sintered $0.98Pb(Zr_{0.54} Ti_{0.46})O_{3.0.02}LaMnO}3$ is similar to that of commercial PZT 6A. Microstructure investigation shows that part of sintering process of $Pb(Zr, Ti)O_3$.$LaMnO_3$ system progresses via liquid phase sintering. It is believed that the evaporation of PbO in PZT sintering is restricted by the addition of $LaMnO_3$ due to the above phenomena. Furthermore the solid solution of $LaMnO_3$ in PZT causes diffuses phase transition.

• Korean Journal of Materials Research
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• v.6 no.1
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• pp.90-98
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• 1996

Mn((Cu0.66AI0.34)1-x(Bi0.3Sb0.7)x) 및 Mn((Fe0.66AI0.34)1-x(Bi0.3Sb0.7)x) 합금계의 상의 변화와 자기적 특성을 조사하였다. Mn((Cu, SI)(Bi, Sb)) 합금계는 Bi상, MnSb상, MnBi상, k-상, Heuser상, Mn2Sb 및 $\beta$-Mn상의 혼합상으로 이루어졌으며 x가 증가함에 따라 Bi상과 Mn2Sb상이 증가하고 K-상, Heusler상 및 $\beta$-Mn상이 줄어들거나 사라졌다. 자기적 성질은 자성을 띄는 MnSb상, MnBi상, Mn2Sb상, k-상 및 Hseusler상과 비자성인 Bi상과 $\beta$-Mn상의 상대적 분율에 의해 결정됨을 알 수 있었고, 150K-200K 부근에서 그 이하로 온도가 감소함에 따라 자화값이 급격히 감소하는 현상이 나타났다. Mn((Fe, AI)(Bi, Sb))합금계는 Bi상, MnSb상, MnBi상, MnBi상,$\beta$-Mn상, k-상 및 Mn2Sb상의 혼합상으로 나타났으며, 자기적 성질은 조사한 전 조성에서 강자성을 띄고 있음을 알 수 있었다.

• Korean Journal of Materials Research
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• v.11 no.6
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• pp.498-501
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• 2001

The effects of MnO$_2$ addition on the piezoelectric properties in 0.9Pb($Mg_{1/3}Nb_{2/3}$)$O_3$-0.1Pb$TiO_3$ relaxor ferroelectrics were studied in the ferroelectricity-dominated temperature range from -4$0^{\circ}C$ to 3$0^{\circ}C$. Dielectric, piezoelectric properties and electric-field- induced strain were examined to clarify the effect of MnO$_2$ addition. As the added amount of MnO$_2$ increase. dielectric and piezoelectric properties of Pb(Mg$_{1/3}$ Nb$_{2/3}$O$_3$ became harder. From the experimental results, it was suggested that Mn behaves as a ferroelectric domain pinning element.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.13 no.2
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• pp.63-67
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• 2003

Synthesis of $PbLaTiO_{3}$ : Mn powders containing La and Mn was carried out using $PbO,\;TiO_{2},\;La_{2}O_{3}\;and\;MnO_{2}$ as starting materials by hydrothermal method. In the synthesis of single phase $PbLaTiO_{3}$ : Mn powder containing La and Mn, the optimal x value corresponding to La substitution was 0.01 which corresponds to $0.99(Pb_{1-x}La_{2x/3}TiO_{3})+0.01MnO_{2}$. The optimal conditions for the preparation of the powder synthesis were 8 M-KOH solvent of hydrothermal solvent, $270^{\circ}C$ of reaction temperature and 24 hrs of run time. It was found that the synthesized powders had spherical morphology with average particle size of 70 nm and specific surface area of $5.5\;m^{2}/g$.

• Applied Chemistry for Engineering
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• v.35 no.1
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• pp.1-7
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• 2024

Mn-M/Al₂O₃ (M = Cu, Fe, Co, and Ce) catalysts were prepared for simultaneous oxidation of NO, CO, and CH₄, and their oxidation activities were compared. The Mn-Cu/ Al₂O₃ catalyst with the best simultaneous oxidation activity was characterized by XRD, Raman, XPS, and O₂-TPD analysis. The result of XRD indicated that Mn and Cu existed as complex oxides in the Mn-Cu/Al₂O₃ catalyst. Raman and XPS results showed that electron transfer between Mn ions and Cu ions occurred during the formation of the Mn-O-Cu bond in the Mn-Cu/Al₂O₃ catalyst. The XPS O 1s and O₂-TPD analyses showed that the Mn-Cu/Al₂O₃ catalyst has more adsorbed oxygen species with high mobility than the Mn/Al₂O₃ catalyst. The high simultaneous oxidation activity of the Mn-Cu/Al₂O₃ catalyst is attributed to these results. Gas-phase NO promotes the oxidation reactions of CO and CH₄ in the Mn-Cu/Al₂O₃ catalyst while suppressing the NO oxidation reaction. These results were presumed to be because the oxidized NO was used as an oxidizing agent for CO and CH₄. On the other hand, the oxidation reactions of CO and CH₄ competed on the Mn-Cu/Al₂O₃ catalyst, but the effect was not noticeable because the catalyst activation temperature was different.

• Korean Journal of Materials Research
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• v.17 no.4
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• pp.203-206
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• 2007

Effects of doping rare earth elements on Ln site of $Ln_{0.7}Ca_{0.3}MnO_3$ (Ln = N d, Sm and La) were examined from structure, magnetic and electrical properties. Size of a-axis increased as following order of La < Nd < Sm, whereas c-axis was not much changed. Curie temperatures of 170 K for $Nd_{0.7}Ca_{0.3}MnO_3$, 110 K for $Sm_{0.7}Ca_{0.3}MnO_3$ and 250 K for $La_{0.7}Ca_{0.3}MnO_3$ were obtained. This result coincides with change of Mn-O bond length causing by a-axis lattice constant. The highest magnetroresistance ratios were 22% at 77 K for $Sm_{0.7}Ca_{0.3}MnO_3$, 32% at 110 K for $Nd_{0.7}Ca_{0.3}MnO_3$, and 33% at 180 K for $La_{0.7}Ca_{0.3}MnO_3$.