• Title/Summary/Keyword: 2nd Sintering

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Sintering and Dielectric Properties of K2O-CaO-P2O5 Glasses-BNT(BaO-Nd2O3-TiO2) Ceramic Composites (K2O-CaO-P2O5계 유리-BNT(BaO-Nd2O3-TiO2)계 세라믹 복합체의 소결 및 유전특성)

  • 오영석;이용수;강원호;정병해;김형순
    • Journal of the Korean Ceramic Society
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    • v.40 no.10
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    • pp.954-960
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    • 2003
  • To develop mobile phone antenna modules, glass-ceramics composites that are 20∼80 dielectric constant materials which has been fabricated. The glass-ceramics composites were based in the BNT (BaO-Nd$_2$O$_3$-TiO$_2$), and properties-a sintering and dielectric property-were investigated in its composites according to the $K_2$O-CaO-P$_2$O$_{5}$ system glass frits. The prepared ceramics were sintered at 900∼120$0^{\circ}C$ with the glass frit contents ranging from 10 to 40 wt%. The shrinkage and relative density grew into increasing glass frits and sintering temperature. Sintered composites showed the tendency that the dielectric constant ($\varepsilon$$_{r}$) and quality factor (Q${\times}$f) decreased in increasing glass frits and sintering temperature.

Dispersion of Silicon Nitride Particles and Sintering Additives of AlN and Nd$_2$O$_3$ in Nonaqueous Suspending Media (비수계분산매체에서 질화규소와 소결첨가제 AlN 및 Nd$_2$O$_3$의 분산)

  • 김재원;백운규;윤경진
    • Journal of the Korean Ceramic Society
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    • v.36 no.2
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    • pp.210-219
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    • 1999
  • The fundamental dispersion property of Si2N4 and a combination of AlN and Nd2O3 as sintering additives in a variety of organic solvents such as alcohols, hydrocarbons, ketones, and ethers was investigated. The stabilization mechanism and interaction between organic functional groups of the various organic additives were studied to clarify the dispersibility of the ceramic particles in the nonaqueous suspending medium. characterization of the suspensions was based mainly on electrokinetic sonic amplitude(ESA) measurements and the flow curves obtained from the rheological studies as well as estimated Hamaker constants. It was found that the contribution of electrostatic repulsive forces to the Si3N4, AlN and Nd2O3 stabilization in organic media is appreciably greater than anticipated and is dependent on the physicochemical properties of organic solvents.

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Electrical Switching Mechanism of the Sintering Oxides (산화물 소결체에서 전기적 Switching 기구)

  • 조동산;김화택
    • Journal of the Korean Ceramic Society
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    • v.15 no.3
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    • pp.135-139
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    • 1978
  • Sintering oxide which was prepared by sintering at $1200^{\circ}C$ the mixture of ${\gamma}$-$Fe_2O_3$ and $Sb_2O_3$ in 2 : 1 mol ratio, showed 1st electrical switching and stable 2nd switching when D.C. voltage was applied. This electrical switching mechanism was known to be thermal mechanism from dependence of environmental temperature of threshold Voltage(Vm), Current(Im) and the conductivity of the current filament of the sintering oxide.

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Improvement of the Magnetic Properties of (Nd, Dy)-Fe-B Sintered Magnets by Modification of HD and Annealing Processes (HD 처리 및 열처리공정 개선에 의한 (Nd, Dy)-Fe-B 소결자석의 자기특성 향상)

  • NamKung, S.;Lee, Y.H.;Kim, M.K.;Jang, T.S.
    • Journal of Powder Materials
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    • v.17 no.5
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    • pp.359-364
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    • 2010
  • In an attempt to optimize the magnetic properties of (Nd, Dy)-Fe-B sintered magnets, hydrogenation and post-sintering heat treatment processes were investigated at various hydrogenation temperatures and heat treatment temperatures. The coercivity of (Nd, Dy)-Fe-B sintered magnets hydrogenated at $400^{\circ}C$ increased to about 1.2 kOe without any detrimental effect on the remanence. Moreover, the coercivity of the magnets was enhanced further by a consecutive $2^{nd}$ and $3^{rd}$ step heat treatment. These results eventually leaded to the reduction of the Dy content in a high coercive (> 30 kOe) (Nd, Dy)-Fe-B sintered magnets, as much as 10%.

Sintering of Nd-Fe-B Magnets from Dy Coated Powder

  • Kim, Jin Woo;Kim, Young Do
    • Journal of Powder Materials
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    • v.20 no.3
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    • pp.169-173
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    • 2013
  • High-coercive (Nd,Dy)-Fe-B magnets were fabricated via dysprosium coating on Nd-Fe-B powder. The sputtering coating process of Nd-Fe-B powder yielded samples with densities greater than 98%. $(Nd,Dy)_2Fe_{14}B$ phases may have effectively penetrated into the boundaries between neighboring $Nd_2Fe_{14}B$ grains during the sputtering coating process, thereby forming a $(Nd,Dy)_2Fe_{14}B$ phase at the grain boundary. The maximum thickness of the Dy shell was approximately 70 nm. The maximum coercivity of the Dy sputter coated samples(sintered samples) increased from 1162.42 to 2020.70 kA/m. The microstructures of the $(Nd,Dy)_2Fe_{14}B$ phases were effectively controlled, resulting in improved magnetic properties. The increase in coercivity of the Nd-Fe-B sintered magnet is discussed from a microstructural point of view.

The Effect of Glass Addition on the Sintering and Dielectric Properties of BaO-Nd2O3-TiO2 Microwave Ceramics (Glass첨가에 의한 BaO-Nd2O3-TiO2계 세라믹스의 저온소결과 마이크로파 유전특성)

  • Shin, Dong-Soon;Choi, Young-Jin;Park, Jae-Hwan;Nahm, Sahn;Park, Jae-Gwan
    • Journal of the Korean Ceramic Society
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    • v.40 no.1
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    • pp.98-103
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    • 2003
  • The effect of glass addition on the low-temperature sintering and microwave dielectric properties in $BaO-Nd_2O_3-TiO_2$ dielectric ceramics were studied. When 10~30 wt% of alkali lithium borosilicate glass was added, the sintering temperature decreases from $1300^{\circ}C$;to;1000^{\circ}C$ and the relative density more than 95% was obtained. When the added amount of glass increased above 10 wt%, the density as well as dielectric properties changed, which was attributed to the second phase formation. When the sample was sintered at 100$0^{\circ}C$ with l0wt% of glass, the dielectric properties of $Qxf_o{ge}2800,;{varepsilon}_r{ge}65;and;{ au_f=+55 ppm/^{\circ}C$ were obtained.

The Effect of Calcination Temperature on Physical Properties of $Ba[Mg_{1/3}(Nb_{0.2}Ta_{0.8})_{2/3}]O_3$ Ceramics (하소온도가 $Ba[Mg_{1/3}(Nb_{0.2}Ta_{0.8})_{2/3}]O_3$ 세라믹스의 물리적 특성에 미치는 영향)

  • 김재윤;김부근;김강언;정수태;조상희
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 1999.11a
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    • pp.252-255
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    • 1999
  • The effect of calcination temperature(1st and 2nd calcining at 110$0^{\circ}C$ , 120$0^{\circ}C$ and 130$0^{\circ}C$ respectively) on physical properties of BMNT Ceramics ware investigated. The optimum 1st and 2nd calcination temperature were 120$0^{\circ}C$ , and sintering temperature was 155$0^{\circ}C$. In this condition, the sintering density was 7.53 [g/㎤] and the dielectric constant, Q.f$_{0}$ and $\tau$$_{r}$ were 26, 80, 300[GHz] and +1.5[ppm/$^{\circ}C$] respectively in the microwave range.e.e.

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Inward Diffusion of Tb Ions and the Magnetic Properties of the Nd-Fe-B Magnets (열처리 조건에 따른 Tb이온의 확산 및 Nd-Fe-B 자석의 자기적 특성)

  • Oh, Seong-Uk;Kim, Dong-Whan;Gong, Gun-Seung;Heo, Young-Woo;Kim, Jeong-Joo;Lee, Joon-Hyung
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.30 no.1
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    • pp.27-31
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    • 2017
  • In this study, the effect of Tb inward diffusion on the magnetic properties of the Nd-Fe-B sintered magnets was studied. After sintering of the magnets, $TbF_3$ slurries were dip-coated on the surface of the samples, then heat-treatment was followed for $TbF_3$ diffusion. The element distribution in the magnets and the diffusion profiles of Tb ions were analyzed by an EPMA (electron probe micro-analyzer). Prolonged heat treatment resulted in a deeper diffusion length of Tb ions. Coercivity of the $1^{st}$ heat-treated sample showed 21.86 kOe, while that of the $1^{st}$, $2^{nd}$ heat-treated and annealed sample revealed 34 kOe.

The Electrical Properties with variation of ZnO Varistors with added of $Nd_2O_3$ ($Nd_2O_3$를 첨가한 ZnO Varistor의 전기적 특성)

  • Cho, Hyun-Moo;Lee, Sung-Gap
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2004.07b
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    • pp.603-606
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    • 2004
  • ZnO varistor ceramics were fabricated with variation of addition of $Nd_2O_3$ amount and the sintering temperature was $l150^{/circ}C$. The average grain sizes were showed decreased from $13.8{\mu}m$ to $4.7{\mu}m$, and varistor voltages were increased from 398 V to 657 V by added amount of $Nd_2O_3$. Nonlinear coefficient a of all were with increasing the amount of $Nd_2O_3$ more than 60, in case of added on 0.1mol% $Nd_2O_3$ was 87. And leakage current were less than $1_{\mu}A$ with applied at 82% of varistor voltage. The clamping voltage ratio of the specimes added 0.1mol% $Nd_2O_3$ was 1.38 at applied 25A [$8/20{\mu}s$]. In the specimen added 0.1mol% $Nd_2O_3$, endurence of surge current and deviation of varistor voltage were 7000A/$cm^2$, $\Delta-2.08%$, respectively.

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Variation in optical, dielectric and sintering behavior of nanocrystalline NdBa2NbO6

  • Mathai, Kumpamthanath Chacko;Vidya, Sukumariamma;Solomon, Sam;Thomas, Jijimon Kumpukattu
    • Advances in materials Research
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    • v.2 no.2
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    • pp.77-91
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    • 2013
  • High quality nanoparticles of neodymium barium niobium ($NdBa_2NbO_6$) perovskites have been synthesized using an auto ignition combustion technique for the first time. The nanoparticles thus obtained have been characterized by powder X-ray diffraction, thermo gravimetric analysis, differential thermal analysis, Fourier transform infrared spectroscopy, Raman spectroscopy and transmission electron microscopy. UV-Visible absorption and photoluminescence spectra of the samples are also recorded. The structural analysis shows that the nano powder is phase pure with the average particle size of 35 nm. The band gap determined for $NdBa_2NbO_6$ is 3.9 eV which corresponds to UV-radiation for optical inter band transition with a wavelength of 370nm. The nanopowder could be sintered to 96% of the theoretical density at $1325^{\circ}C$ for 2h. The ultrafine cuboidal nature of nanopowders with fewer degree of agglomeration improved the sinterability for compactness at relatively lower temperature and time. During the sintering process the wide band gap semiconducting behavior diminishes and the material turns to a high permittivity dielectric. The microstructure of the sintered surface was examined using scanning electron microscopy. The striking value of dielectric constant ${\varepsilon}_r=43$, loss factor tan ${\delta}=1.97{\times}10^{-4}$ and the observed band gap value make it suitable for many dielectric devices.