• Journal of Magnetics
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• 제2권1호
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• pp.28-33
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• 1997

Very large in electrical resistivity by several orders of magnitude is obtained when an external magnetic field is applied to the colossal magnetoresistnace (CMR) materials such as La-Ca-Mn-O. The magnetoresistance is strongly temperature-dependent, and exhibits a sharp peak below room temperature, which can be shifted by adjusting the composition or processing parameters. The control of lattice geometry or strain, e.g., by chemical substitution, epitaxial growth or post-deposition anneal of thin films appears to be crucial in obtaining the CMR properties. The orders of magnitude change in electrical resistivity could be useful for various magnetic and electric device applications. .

• 한국전기전자재료학회논문지
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• 제19권5호
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• pp.417-421
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• 2006

In this study, in order to develop low temperature sintering piezoelectric ceramics for LTCC (Low-Temperature Cofired Ceramic) multilayer piezoelectric actuator, PMW-PMN-PZT ceramics using $0.2wt%\; Li_2CO_3$ and $0.25wt%\;CaCO_3$ as sintering aids were investigated according to the varation of PMW substution. Composition ceramics could be sintered at $900^{\circ}C$ by adding sintering aids. As the amount of PMW substitution increased, the crystal structure of PMW-PMN-PZT ceramics moved from tetragonal phase to rhombohedral phase gradually, and MPB(Morphotrophic Phase Boundary) region appeared at 2 mol% PMW substitution. At the sintering temperature of $900^{\circ}C$, the density, electromechanical coupling factor(kp), mechanical quality factor(Qm), dielectric constant(${\epsilon}r$), piezoelectric constant(d33) and Curie temperature(Tc) of 2 mol% PMW substituted PMW-PMN-PZT ceramics showed the optimal values of $7.88g/cm^3$, 0.58, 1002, 1264, 352 pC/N and $336^{\circ}C$, respectively, for LTCC multilayer piezoelectric actuator application.

• 한국재료학회지
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• 제14권9호
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• pp.655-658
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• 2004

Lithium ferrites are a low-cost material which have been prominent in the high frequency core industry because of their excellent temperature performance and high squareness ratio. In order to develope the lithium ferrites with the high squareness and low coercive force, the ferrites of $Li_{0.48}Bi_{0.02}Ni_{0.04}Fe_{2.46-x}O_4$ were investigated the by varying composition, temperature and frequency. Electric loss of the Li-ferrite was lowered with the substitution of $Mn_{2}O_3$. The addition of $Mn_{2}O_3$ increased the magnetic induction (Bm&Br) but decreased the coercive force (Hc) and the squareness ratio (R=Br/Bm). Also, the Br value was stable at environmental temperature variation.

• Journal of Magnetics
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• 제18권4호
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• pp.405-411
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• 2013

The structural, magnetic and magnetocaloric properties of $CoMn_{1-x}Cr_xGe$ (x=0.05-0.125) have been investigated by using electron microscopy, x-ray diffraction, calorimetric and magnetic measurements. In this study, our aim is to justify the magnetocaloric effect by tuning the structural and magnetic transition temperature with Cr doping on CoMnGe pure system. The substitution of Cr for Mn leads to a decrease of both structural and magnetic transition temperatures. However, structural and magnetic transition temperatures do not close to each other. From magnetization measurement, we calculate that isothermal entropy change associated with magnetic transition can be as high as 3.82 J $kg^{-1}K^{-1}$ at 302 K in a field of 7 T. Meanwhile, structural phase transition contribution to isothermal entropy change is calculated as 5.85 J $kg^{-1}K^{-1}$ at 322 K for 7 T.

• Journal of Magnetics
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• 제14권2호
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• pp.93-96
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• 2009

The Mn-substituted M-type Ba-ferrite ($BaFe_{12-x}Mn_xO_{19}$; x = 0, 2, 4, 6) powders were prepared by the HTTD (High Temperature Thermal Decomposition) method. The effect of $Mn^{3+}$ Jahn-Teller ions on the magnetic properties has been studied by x-ray diffraction, vibrating sample magnetometry, and $M{\ddot{o}}ssbauer$ spectroscopy. With increasing Mn substitution, the lattice parameter $a_0$ increases while $c_0$ decreases. The magnetocrystalline anisotropy constants ($K_1$) were determined as 2.9, 2.2, 1.8, and, $1.3{\times}10^6\;erg/cm^3$ for x = 0, 2, 4, and 6, respectively, by the LAS method. We have studied the change of cation distribution by $M{\ddot{o}}ssbauer$ spectroscopy which is closely related to $K_1$.

• 한국전기전자재료학회논문지
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• 제17권5호
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• pp.492-496
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• 2004

In this study, (0.96 －x)(PSN-PZT)－xBF－0.04 PNW＋0.3wt%MnO$_2$＋0.6wt%CuO ceramics were fabricated with the variations of the amount of BiFeO$_3$substitution and sintering temperature for the development of modified ceramics which can be sintered in the low temperature($\leq$100$0^{\circ}C$ ), and their microstructural, dielectric and piezoelectric characteristics were investigated. As the amount of BiFeO$_3$ substitution was increased, the density, mechanical quality factor(Q$_{m}$) and electromechanical coupling factor(k$_{p}$) showed the maximum value at each of sintering temperature. At sintering temperature of 98$0^{\circ}C$ and BiFeO$_3$substitution of 2 mol%, the density, dielectric constant and electromechanical coupling factor(k$_{p}$) showed the maximum value of 7.84 g/㎤, 1415 and 0.49, respectively. And at sintering temperature of 95$0^{\circ}C$ and BiFeO$_3$substitution of 3mol%, mechanical quality factor showed the maximum value of 1062. 1062.

• 한국전기전자재료학회논문지
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• 제29권9호
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• pp.539-545
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• 2016

Alumina added with Mn3O4 up to 7.5 cat% of Mn was prepared by conventional ceramic processing, and the sintering behavior and the optical properties of which were studied as functions of Mn content. Densification and grain growth of alumina were enhanced by Mn addition up to 0.75 cat% but was leveled off at higher concentrations. XRD revealed that $Al_2MnO_4$(galaxite) was formed as a second phase in the specimens with more than 0.75 cat% of Mn. Thus it is believed that either the solid solution effect of Mn or the Zener effect of $Al_2MnO_4$ becomes predominant in the sintering of Mn-added $Al_2O_3$ according to the additive concentration. UV-VIS reflectivity(SCI) spectra of Mn-added $Al_2O_3$ consisted of smooth bottoms in 300~550 nm wavelength range and plateaus at wavelengths longer than 650 nm. The reflectivity spectrum continuously moved downward, and the specimen color became darker and thicker with increasing Mn content. The CIELAB color change with respect to standard white was also dependent on the amount of Mn added: ${\Delta}L^*$(D65) negatively increased and ${\Delta}E_{ab}^*$(D65) positively increased with increasing Mn content, probably due to Mn substitution to Al and/or the mixing effect of black $Al_2MnO_4$ as a second phase.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2007년도 추계학술대회 논문집
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• pp.293-293
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• 2007

현재 활발하게 진행되고 있는 이차전지 양극 물질 중 저렴한 가격과 친환경성으로 각광받고 있는 $LiMn_2O_4$ spinel 산화물은 여러 장점에도 불구하고 용량 값이 기존 알려져 있던 Co-계 산화물에 비해 떨어지고 cycle 특성 역시 현저하게 이어진다. 이는 Mn이 전해액과의 반응에 있어 구조적인 안정성을 지니지 못하여 용출되어 나타나는 특성이다. 이번 연구에서는 Mn의 용출을 저지하고 용량의 향상을 이룰 수 있는 전이금속 중 Fe산화물을 치환하여 구조적 안정성을 갖도록 하였다. Fe산화물 치환을 통해 기본적 물성의 변화와 전기적 특성 변화를 측정하였고 공정에서의 온도 및 입도에 따른 영향도 확인하였다. Fe산화물은 Mn 자리의 3+와 4+의 자리에 치환되어 용량을 증대시키고 사이클 특성을 10회 기준으로 20%가량 향상시키는 효과를 가져왔다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 춘계학술대회 논문집 반도체 재료 센서 박막재료 전자세라믹스
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• pp.161-164
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• 2004

In this study, to develop the composition ceramics for the Ultrasonic vibrator, $Pb(Mn_{1/3}Nb_{2/3})O_3Pb(Zr.Ti)O_3$ system ceramics were manufactured as a function of PCN substitution. Its dielectric and piezoelectric characteristics were investigated. With increasing the amount of PCN substitution, electromechanical coupling factor(kp) were increased until 3mol% PCN and that after decreased. mechanical quality factor(Qm) showed the maxinum value at 2mol% PCN. Eletromechanical coupling factor, mechanical quality factor and dielectric constant were showed optimum value at PCN 2mol% as 0.58, 1630 and 1407, respectively for ultrasonic vibrator applications.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 제38회 하계학술대회
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• pp.1337-1338
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• 2007

In this study, in order to develop low temperature sintering ceramics for multilayer piezoelectric actuator, 0.07Pb$(Mn_{1/3}Nb_{2/3})O_{3}-xPb(Ni_{1/3}Nb_{2/3})O_{3}-(0.93-x)Pb(Zr,Ti)O_{3}$ ceramics system were fabricated using $Li_{2}CO_{3}-Bi_{2}O_{3}$-CuO sintering aids and the specimens were sintered at $930^{\circ}C$. Thereafter their piezoelectric and dielectric characteristics were investigated with the amount of PNN substitution. At 9[mol%] PNN substitution, electromechanical coupling factor (kp), mechanical quality factor (Qm) and piezoelectric constant ($d_{33}$) showed the optimum value of 0.60, 1323 and 387pC/N, respectively.