• The Transactions of the Korean Institute of Electrical Engineers C
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• v.53 no.2
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• pp.67-72
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• 2004

The microwave dielectric properties and microstructure of the (1-x)$Mg_4Ta_2O_{9-x}TiO_2$(X=0, 0.3, 0.4) ceramic were, investigated. The specimens were prepared by the conventional mixed oxide method with sintering temperature of $1350^{\circ}C$∼$1425^{\circ}C$. According to the XRD patterns, the (1-x)$Mg_4Ta_2O_{9-x}TiO_2$(X=0, 0.3, 0.4) ceramics have the $Mg_4Ta_2O_{9}$ phase(hexagonal). The dielectric constant($\varepsilon$$_{\gamma}$) and density increased with sintering temperature and mole fraction of x. To improve the quality factor and the temperature coefficient of resonant frequency, TiO$_2$($\varepsilon_{r}$=100, $Q{\times}f_{r}$=40,000GHz, $\tau$$_{f}$=＋450 ppm/$^{\circ}C$) was added in $Mg_4Ta_2O_{9}$ ceramics. In the case of the $0.7Mg_4Ta_2O_{9}$-$0.3TiO_2$ and the $0.6Mg_4Ta_2O_{9}$-$0.4TiO_2$ceramics sintered at $1400^{\circ}C$ for 5hr., the microwave dielectric properties were $\varepsilon$$_{\gamma}$=11.72, $Q{\times}f_{r}$=126,419GHz, $\tau_{f}$=-31.82 ppm/$^{\circ}C$ and $\varepsilon_{r}$=12.19, $Q{\times}f_{r}$=109,411GHZ, $\tau$$_{f}$= -17.21 ppm/$^{\circ}C$, respectively.

• Journal of the Korean Magnetics Society
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• v.19 no.3
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• pp.106-112
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• 2009

$Ni_{1-x}Mg_xFe_2O_4$ ferrite system was studied by using X-ray diffraction and $M{\ddot{o}}ssbauer$ spectroscopy. The samples were prepared by ceramic sintering method with Mg content x. The X-ray diffraction patterns of samples show phase of cubic spinel structure. There are no remarkable changes of lattice constants in $Ni_{1-x}Mg_xFe_2O_4$ ferrite system. The $M{\ddot{o}}ssbauer$ spectra were consisted of two sets of six lines, respectively, corresponding to $Fe^{3+}$ at tetrahedral and octahedral sites. The magnetic hyperfine field of samples was decreased as increasing Mg contents x in both sites and it was shown Yafet-Kittel magnetic structure. $NiFe_2O_4$ was shown complete inverse spinel, but $NiFe_2O_4$ was shown partial inverse spinel which absorption area ratio (oct/tet) was 1.449 in $M{\ddot{o}}ssbauer$ spectrum.

• Journal of the Korean Institute of Navigation
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• v.22 no.4
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• pp.69-75
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• 1998

The super wideband electromagnetic wave absorber in RF-A-PF type has been proposed, which can be used for an anechoic chamber, wall material to prevent TV ghost, etc, In this paper, $Ni_x-Mg_{0.1}-Zn_(1-x-0.1){\cdot}Fe_2O_4$ Ferrite Powder has been fabricated. Using this, then, [$Ni_x-Mg_{0.1}-Zn_(1-x-0.1){\cdot}Fe_2O_4$-Rubber composite for RF-layer in the RF-A-PF type absorber has been fabricated and its characteristics has been analyzed. As a result, it has been shown that the $Ni_x-Mg_{0.1}-Zn_(1-x-0.1){\cdot}Fe_2O_4$-Rubber composit with the quantity $_x$ of $Ni_x$ between 0.5 and 0.6 is suitable for the RF-layer in the case of which the grain size is sub-micrometer order.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.7
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• pp.718-723
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• 2004

Crystal structure of $(Ba-{1-x}La_x)[Mg_\frac{1+x}{3}}Nb_\frac{{2-x}{3}}]O_3$ (BLMN) ceramics with 0\leq1x \geq was investigated using synchrotron X-ray powder diffraction (XRD) and high reso(B $a_{l-x}$L $a_{x}$)[M $g_{(1+x)}$3/N $b_{(2-x)/3}$］ $O_3$lution transmission electron microscopy (HRTEM). When the La content, x, is above 0.1, the 1:2 ordered hexagonal structure found in Ba($Mg_\frac{1}{3}Nb_\frac{2}{3}})O_3$(BMN) was transformed into 1:1 ordered cubic structure. The 1:1 ordered cubic structure was maintained up to x=0.7. When x exceeded 0.7, however, BLMN was transformed into 1:1 ordered structure which has cation displacement and in-phase and anti-phase tilt of octahedra.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.392-393
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• 2007

PDP용 녹색 $Zn_2SiO_4$:Mn 형광체의 발광특성과 결정성을 향상시키기 위해 co-dopant로 Mg를 첨가한 $(Zn_{1-x}Mg_x)_2SiO_4$:Mn 형광체를 합성하였다. 합성된 형광체의 발광특성을 PL로 조사한 결과, $Zn_2SiO_4$:Mn 형광체는 Mg의 농도에 관계없이 530nm에서 녹색 발광을 하였고, Mg의 농도가 0.5 mol%일 때 가장 높은 발광세기가 나타났다. 이것은 Zn과 이온반경이 비슷한 Mg가 치환되어 모체에서의 Mn으로의 에너지 전이가 증가하여 발광세기가 증가한 것으로 생각된다.

• Journal of the Korean Ceramic Society
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• v.34 no.2
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• pp.175-180
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• 1997

새로운 복합페로브스카이트계 고용체 (1-x)Ba(Mg1/3Ta2/3)O3-xLa(Mg2/3Ta1/3)O3(x=0.0-1.0)를 설계하고 조성에 따른 고용체의 결정구조의 변화 및 MPB(Morphotropic Phase Boundary)를 분말 XRD를 이용하여 분석하였다. 초격자회절선의 변화로부터 MBT에 10mol%의 LMT를 치환함에 따라 1:2에서 1:1로의 규칙화타입의 전이가 일어남을 알 수 있었다. 면심입방정구조 영역(0.10.8조성의 경우, 주회절선의 피이크분리 및 새로운 회절선들로부터 격자비틀림의 형태가 단사정임을 알 수 있었다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.300-301
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• 2007

$Mg_4(Nb_{2-x}V_x)O_9$ (MNV) ceramics have been prepared by a hydrothermal method. Low-temperature sintering of $Mg_4(Nb_{2-x}V_x)O_9$ (MNV) by V substitution for Nb was discussed in this study. A $Q{\cdot}f_0$ value of 103,297 GHz with a ${\varepsilon}_r$ of 12.56 and a ${\tau}_f$ of $-10.53\;ppm/^{\circ}C$ was obtained when x=0.0625 after sintering at $1100^{\circ}C$ for 5 h.

• Journal of Powder Materials
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• v.22 no.5
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• pp.344-349
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• 2015

$MgB_2$ bulk superconductors are synthesized by the solid state reaction of ($MgB_4$+xMg) precursors with excessive Mg compositions (x=1.0, 1.4, 2.0 and 2.4). The $MgB_4$ precursors are synthesized using (Mg+B) powders. The secondary phases ($MgB_4$ and MgO) present in the synthesized $MgB_4$ are removed by $HNO_3$ leaching. It is found that the formation reaction of $MgB_2$ is accelerated when Mg excessive compositions are used. The magnetization curves of $Mg_1+_xB_2$ samples show that the transition from the normal state to the superconducting state of the Mg excessive samples with x=0.5 and x=0.7 are sharper than that of $MgB_2$. The highest $J_c-B$ curve at 5 K and 20 K is achieved for x=0.5. Further addition of Mg decreases the $J_c$ owing to the formation of more pores in the $MgB_2$ matrix and smaller volume fraction of $MgB_2$.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.5 no.2
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• pp.152-164
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• 1995

$xPb(Fe_{1/2}Nb_{1/2})O_3 - (1 - x)Pb(Mg_{1/3}Nb_{2/3})O_3$ powders were synthesized by the molten salt synthesis method using the NaC!- KCI flux with 1 : 1 molar ratio, and their powders and dielectric properties were investigated. The synthesized powders showed less agglomerated shape with the average particle size of less than $2 \mu\textrm{m}$. The composition $x0.3Pb(Fe_{1/2}Nb_{1/2})O_3-0.7Pb(Mg_{1/3}Nb_{2/3})O_3$ could be sintered at $1000{\times}C$ and its dielectric constnat was over 11, 000.

• Progress in Superconductivity and Cryogenics
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• v.16 no.1
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• pp.19-22
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• 2014

The effects of Mg content on the pore formation, density and critical properties were investigated in in-situ reacted $MgB_2$ superconductors. The $Mg_{1+x}B_2$, (x=-0.2, 0.0, 0.05, 0.3, 1.0) bulk samples with different Mg contents were heat-treated at $900^{\circ}C$ for 1 h in an Ar atmosphere. The dimensional changes of a pellet's mass and volume after heat-treatment were measured. After heat-treatment process, the sample mass was decreased by Mg evaporation, but the sample volume was expanded by pore formation at the Mg site; therefore, the apparent density was decreased. Spherical pores the same as Mg particles were developed after heat-treatment in all samples, and the pore density was increased with increasing Mg content. As the x of Mg content was increased to 1.0, the apparent density of $Mg_{1+x}B_2$ samples was decreased due to a relatively larger reduction in a mass change. The critical current density of Mg excessive sample of x=0.05 showed the highest values over the applied magnetic fields because the excessive Mg may compensate Mg loss and enhance grain connectivity.