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Zr-2.5wt.% Nb 합금의 인장강도 특성

$M\""{o}ssbauer$ Effet Studies on Nanocrystalline $Fe_{73.5}Cu_{1}Nb_{3}Si_{16.5}B_6$ Alloy (초미세결정립 $ Fe_{73.5}Cu_{1}Nb_{3}Si_{16.5}B_6$ 합금의 $M\""{o}ssbauer$ 효과 연구)

  • 신영남;김재경;양재석;조익한;강신규
    • Journal of the Korean Magnetics Society
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    • v.4 no.1
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    • pp.12-19
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    • 1994
  • The crystallization behavior of the amorphous $Fe_{73.5}Cu_{1}Nb_{3}Si_{16.5}B_{6}$ alloy with isothermal annealing at $552^{\circ}C$ was studied by $M\"{o}ssbauer$ spectroscopy. The amorphous phase was revealed to coexist together with $Do_{3}-FeSi$ nanocrystalline and Cu-duster in annealed alloys by $M\"{o}ssbauer$ spectrum analysis. At the early stage of crystallization, Si content of FeSi is high due to the creation of Cu-cluster, and decreases with annealing until 60 minutes, which results in the increase in the mean hyperfine field of FeSi, and thereafter keeps constant. After 60 minutes, the decrease in the mean hyperfine field of the residual armrphous, in spite of a slight change in the volume fraction of the FeSi and the residual armrphous, is caused by the increase in the content of Nb and B in residual amorphous phase. Both directions of the hyperfine field, those of the FeSi and the residual amorphous, become randomly oriented in about 60 minutes. For FeSi and Cu-duster, the Avrami exponents are 0.51 and O.65, the activation energies are 2.35 eV and 2.44 eV, and the incubation times are 2.4 minutes and 0.8 minutes respectively. Earlier formation of Cu-duster than that of FeSi is coincidence with the fact that Cu atom promotes the nucleation of the FeSi.

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Dielectric and Piezoelectric Properties of [Li0.04(Na0.5K0.5)0.96](Nb0.86Ta0.10Sb0.04)O3 Ceramics Doped with SrO (SrO의 첨가에 따른 [Li0.04(Na0.5K0.5)0.96](Nb0.86Ta0.10Sb0.04)O3세라믹스의 유전 및 압전 특성)

  • Park, Min-Ho;Yoo, Ju-Hyun
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.25 no.3
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    • pp.198-203
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    • 2012
  • In this study, $[Li_{0.04}(Na_{0.5}K_{0.5})_{0.96}](Nb_{0.86}Ta_{0.10}Sb_{0.04})O_3+xSrO$ (x=0, 0.0025, 0.005, 0.0075) ceramics were synthesized by the conventional mixed oxide method. The X-ray diffraction patterns demonstrated that ceramics possessed single perovskite structure. The SEM images indicate that microstructure can be obviously affected by a small amount of added SrO. The phase transition temperature tetragonal-cubic($T_c$) and orthorhombic-tetragonal($T_{o-t}$) shifts downward and upward with the increase of Sr addition, respectively. The excellent piezoelectric properties of $d_{33}=170[pC/N]$, $k_p=0.37$, $Q_m=64.12$, $T_{o-t}=153^{\circ}C$ and $T_c=370^{\circ}C$ were obtained from the 0.25 mol% Sr added ceramics sintered at $1,120^{\circ}C$ for 1 h.

Dielectric Properties and Phase Transformation of Poled <001>-Oriented Pb(Mg1/3Nb2/3)O3-PbTiO3 Single Crystals (분극된 <001> 방위 Pb(Mg1/3Nb2/3)O3-PbTiO3 단결정의 유전 특성 및 상전이)

  • Lee, Eun-Gu;Lee, Jae-Gab
    • Korean Journal of Materials Research
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    • v.22 no.7
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    • pp.342-345
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    • 2012
  • The dielectric properties and phase transformation of poled <001>-oriented $Pb(Mg_{1/3}Nb_{2/3})O_3-x%PbTiO_3$(PMN-x%PT) single crystals with compositions of x = 20, 30, and 35 mole% are investigated for orientations both parallel and perpendicular to the [001] poling direction. An electric-field-induced monoclinic phase was observed for the initial poled PMN-30PT and PMN-35PT samples by means of high-resolution synchrotron x-ray diffraction. The monoclinic phase appears from $-25^{\circ}C$ to $100^{\circ}C$ and from $-25^{\circ}C$ to $80^{\circ}C$ for the PMN-30PT and PMN-35PT samples, respectively. The dielectric constant (${\varepsilon}$)-temperature (T) characteristics above the Curie temperature were found to be described by the equation$(1/{\varepsilon}-1/{\varepsilon}_m)^{1/n}=(T-T_m)/C$, where ${\varepsilon}_m$ is the maximum dielectric constant and $T_m$ is the temperature giving ${\varepsilon}_m$, and n and C are constants that change with the composition. The value of n was found to be 1.82 and 1.38 for 20PT and 35PT, respectively. The results of mesh scans and the temperature-dependence of the dielectric constant demonstrate that the initial monoclinic phase changes to a single domain tetragonal phase and a to paraelectric cubic phase. In the ferroelectric tetragonal phase with a single domain state, the dielectric constant measured perpendicular to the poling direction was dramatically higher than that measured in the parallel direction. A large dielectric constant implies easier polarization rotation away from the polar axis. This enhancement is believed to be related to dielectric softening close to the morphotropic phase boundary.

Heat Treatment Effects of $Fe_{73.0}Cu{1.0}Nb_{3.5}Si_{14.0}B_{7.6}$Alloy with Imbedded Nanocrystalline Phase under Magnetic Field (초미세결정립과 비정질이 공존하는 $Fe_{73.9}$$Cu_{1.0}$$Nb_{3.5}$$Si_{14.0}$$B_{7.6}$ 합금의 자기장 중 열처리)

  • Yang, J.S.;Son, D.;Cho, Y.
    • Journal of the Korean Magnetics Society
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    • v.8 no.1
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    • pp.13-20
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    • 1998
  • The crystallographic and high frequency characteristics of $Fe_{73.9}Cu_{1.0}Nb_{3.5}Si_{14.0}B_{7.6}$ soft magnetic alloys were investigated under the magnetic field annealing. As-cast ribbon with which already imbedded nanocrystalline Fe-Si phase on the surface have a preferred orientation with (400) plane to surface and also with the [011] direction parallel to the ribbon length. The extra nanocrystalline Fe-Si phase appeared throughout at 45$0^{\circ}C$ in samples with or without the longitudinal magnetic field. However the formation of nanocrystalline phase does not appear on the suface layer until 50$0^{\circ}C$ annealing temperature under the transverse field. The cryststallization fraction of annealed samples with longitudinal magnetic field is higher than that of samples without magnetic field. When the transverse magnetic field is applied, the crystallization fraction does not increases but decreases until 50$0^{\circ}C$. However the crystallization of internal regions can be confirmed by X-ray diffraction measurement via tilting the sample. It was found that for all samples, the saturation induction were all same with 1.3 T. The coercive field of as-cast sample was 1.06 A/cm, but in annealed samples it decrease from 0.56 to 0.1 A/cm with increasing annealing temperature from 400 and 55$0^{\circ}C$, respectively. The squareness of annealed samples under transverse magnetic field has a small value than that of both without field and with longitudinal field annealing.

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Electrical and mechanical properties of NiO doped Pb(Ni$_{1}$3/Nb$_{2}$3/)O$_3$-PbTiO$_3$-PbZrO$_3$-ceramics (NiO-Doped Pb(Ni$_{1}$3/Nb$_{2}$3/)O$_3$-PbTiO$_3$-PbZr$_3$-O세라믹스의 전기 및 기계적 특성에 관한 연구)

  • 나은상;김윤호;최성철
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.10 no.3
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    • pp.245-251
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    • 2000
  • Dielectric properties, piezoelectric properties and mechanical properties of NiO-doped Pb($(Ni_{1/3}Nb_{2/3})O_3-PbTiO_3-PbZrO_3$ ceramics were investigated. Powders, prepared by columbite precursor method, were cold pressed and sintered at temperature ranging from $1100^{\circ}C$ to $1250^{\circ}C$. Dielectric constant and piezoelectric constant increased with amount of NiO up to 1 mol% and then decreased with further addition of NiO. It seems that NiO acts as a sintering aid at the sintering temperatures of $1150^{\circ}C$. When the samples were sintered at temperature above $1200^{\circ}C$, however, both dielectric constant and electromechanical coupling factor decreased and mechanical quality coefficient increased with addition of NiO. Hardness and fracture toughness of PNN-PT-PZ increased with addition of NiO up to 1 mol%, and then decreased slightly with further addition of NiO. These results showed that dielectric properties, piezoelectric properties and mechanical properties of PNN-PT-PZ system seemed to be closely related with microstructural factors such as grain size, bulk density and the amount of second phase.

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Mechanical Properties of HfN/Si$_3$N$_4$and NbN/$Si_3N_4$Multilayer Coatings (HfN/Si$_3$N$_4$와 NbN/$Si_3N_4$다층박막의 기계적 특성)

  • Jeong, Jin-Jung;Hwang, Seon-Geun;Lee, Jong-Mu
    • Korean Journal of Materials Research
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    • v.11 no.3
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    • pp.236-242
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    • 2001
  • HfN/Si$_3$N$_4$and NbN/Si$_3$N$_4$ multilayer coatings were deposited onto a high speed tool steel substrate by reactive sputtering and their mechanical properties were evaluated in terms of the dependence of hardness and adhesion strength on the sputter deposition process parameters. The hardnesses of both HfN/Si$_3$N$_4$and NbN/Si$_3$N$_4$ multiplayer coatings increase up to the flux ratio of 0.4 but nearly do not change after that as the $N_2$/Ar flux ratio in nitride sputter deposition increases. The hardnesses of both multiplayer coatings nearly do not change with annealing at low temperatures but decrease owing to oxidation with annealing at a high temperature like 80$0^{\circ}C$ after depositing the layers by sputtering. Post-annealing at low temperatures increases the adhesion strength of the multilayers. but high temperature annealing is not desirable since it decreases the adhesion strength besides the hardness deterioration.

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Ferroelectric domain inversion in $LiNbO_3$ crystal plate during heat treatment for Ti in-diffusion ($Ti:LiNbO_3$ 도파로 제작을 위한 열처리 과정 동안 강유전 도메인 특성에 미치는 영향)

  • Yang, W.S.;Lee, H.Y.;Kwon, S.W.;Kim, W.K.;Lee, H.Y.;Yoon, D.H.
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.15 no.3
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    • pp.124-127
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    • 2005
  • It is demonstrated that the annealing process for Ti in-diffusion to z-cut $LiNbO_3$ at temperature lower than the curie temperature in a platinum (Pt) box can cause a ferroelectric micro-domain inversion at the +z surface and Li out-diffusion, therefore which should be avoided or suppressed for waveguide type periodically poled lithium niobate (PPLN) devices. The depth of the inversion layer depends on the Ti-diffusion conditions such as temperature, atmosphere, the sealing method of $LiNbO_3$ in the Pt box and crystal orientation is experimentally examined. The result shows that the polarization-inverted domain boundary appears at the only +z surface and its thickness is about $1.6{\mu}m$. Also, for the etched $LiNbO_3$, surface the domain shape was observed by the optical microscope and atomic force microscopy (AEM), and distribution of the cation concentrations in the $LiNbO_3$ crystal by the secondary ion mass spectrometry (SIMS).

유전체 재료를 활용한 이동통신 필터 기술

  • 김준철;방규석;이형규
    • The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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    • v.12 no.3
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    • pp.25-34
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    • 2001
  • There are many kinds of dielectric materials in microwave dielectric filters for mobile telecomunication. But It is need to new dielectric materials for IMT200O, Bluetooth, wireless LAN to miniaturize the dielectric filters. These kinds of materials should have high dielectric constants, high Q, and low firing sintering temperature(<900˚C ). Multilayer monolithic dielectric filters are manufactured by BiNb04, dielectric ceramics cofired at 875˚C .

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A Study on the Dielectric and Pyroelectric Properties of the Pb(Sn$_{1}$2/Nb$_{1}$2/)O$_3$-PbTiO$_3$-PbZrO$_3$ Ceramics doped with MnO$_2$ (MnO$_2$가 첨가된 Pb(Sn$_{1}$2/Nb$_{1}$2/)O$_3$-PbTiO$_3$-PbZrO$_3$ 세라믹의 유전 및 초전특성에 관한 연구)

  • 함영욱;이능헌;이덕출
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 1993.11a
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    • pp.10-13
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    • 1993
  • ln this study, x PSN - y PT - z PZ ceramics doped with w MnO$_2$were fabricated by the mixed oxide method at 1250[$^{\circ}C$] for 2[hr] and then the dielectric and pyroelectric properties were investigated. In the 0.05 PSN - 0.4 PT - 0.55 PZ specimen with 0.5[wt.%] MnO$_2$, the pyroelectric coefficient was 6.6${\times}$10$\^$-8/[C/cm$^2$$.$$^{\circ}C$], respectibly.

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