• Title, Summary, Keyword: xBaTiO3-(1-x)CoFe2O4

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Relaxor Behaviors in xBaTiO3-(1-x)CoFe2O4 Materials

  • Dung, Cao Thi My;Thi, Nhu Hoa Tran;Ta, Kieu Hanh Thi;Tran, Vinh Cao;Nguyen, Bao Thu Le;Le, Van Hieu;Do, Phuong Anh;Dang, Anh Tuan;Ju, Heongkyu;Phan, Bach Thang
    • Journal of Magnetics
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    • v.20 no.4
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    • pp.353-359
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    • 2015
  • Dielectric properties of $xBaTiO_3-(1-x)CoFe_2O_4$ composite materials have been investigated. Dielectric properties of $BaTiO_3$, $CoFe_2O_4$ and $0.5BaTiO_3-0.5CoFe_2O_4$ samples show frequency dependence, which is classified as relaxor behavior with different relaxing degree. The relaxor behaviors were described using the modified Curier-Weiss and Vogel-Fulcher laws. Among three above samples, the $BaTiO_3$ sample has highest relaxing degree. Photoluminescence spectral indicated defects, which might in turn control relaxing degree.

Microwave Dielectric Properties of $\textrm{BaCo}_{x}\textrm{Ti}_{x}\textrm{Fe}_{12-2x}\textrm{O}_{19}$($1.0\leq\textrm{x}\leq5.0$) Materials ($\textrm{BaCo}_{x}\textrm{Ti}_{x}\textrm{Fe}_{12-2x}\textrm{O}_{19}$($1.0\leq\textrm{x}\leq5.0$)재료의 Microwave 유전특성)

  • Kim, Chan-Uk;Jo, Nam-Ung
    • Korean Journal of Materials Research
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    • v.8 no.8
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    • pp.775-779
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    • 1998
  • The resonant frequency fo and unloaded quality factor Qu of CoTi-substituted Barium ferrites($\textrm{BaCo}_{x}\textrm{Ti}_{x}\textrm{Fe}_{12-2x}\textrm{O}_{19}$, $1.0\leq\textrm{x}\leq5.0$) were measured at frequencies between 5 to 10GHz using the paralleled copper-plate wave guide method. The measurements showed that the permittivities of CoTi-substituted Barium ferrites(CoTi-BF) increased from 14.7 to 23.4 with the contents of CoTi, x, and the loss tangents had values of $\textrm{10}^{-3}$ order. From these results, CoTi-BF are considered to be very promising materials in microwave devices such as dielctric resonator antennas.

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Properties of ba-ferrite Particles Synthesized by Molten Salt Method (용융염법으로 합성한 Ba-ferrite 입자의 특성)

  • 오영우
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.13 no.6
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    • pp.545-550
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    • 2000
  • In order to synthesize Ba-ferrite particles by molten salt method KCl and NaCl were added to basic composition to 50% by weight. X was varied from 0.0 to 1.0 to control the magnetic properties in $BaFe_{12-2x}$/ $Co_{x}$ / $Ti_{x}$ / $O_{19}$ and 1 mol% of $SiO_2$was added to control the aspect ratio of hexagonal platelets. And the effects of reaction temperatures were examined by varying the temperature from 85$0^{\circ}C$ to 120$0^{\circ}C$ with 5$0^{\circ}C$ intervals. Eutectic composition of NaCl and KCl lowered the crystallizing temperature of Ba-ferrite in molten salts than using KCl and NaCl separatly. The morphology of resulting Ba-ferrite particles was clearly hexagonal-shaped plates. $H_{c}$ and $M_{r}$ were decreased when F $e^{3+}$ was substitued with $Co^{2+}$ and $Ti^{4+}$ from x=0 to x=1.0 in $BaFe_{12-2x}$/ $Co_{x}$ / $Ti_{x}$ / $O_{19}$ . Adding 1mol% $SiO_2$in molten salt method increased the size but shortened c-axis of the hexagonal ferrites and this result is an opposite phenomenon compared with the result in solid-statge reaction.n.ion.n.

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Magnetic and Microwave Absorbing Properties of Ti-and Co-Substituted Barium Ferrite (BaFe12-2X TiXCoXO19)

  • Han-Shin Cho;Yong-Jin Kim;Sung-Soo Kim
    • Journal of Magnetics
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    • v.4 no.2
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    • pp.65-68
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    • 1999
  • The M-type barium ferrite ($BaFe_{12}O_{19}$) is well known magnetic material to be used as a permanent magnet due to its strong uniaxial anisotropy. The substitution of nonmagnetic $Ti^{+4}$ and magnetically weak $Co+^2ion for Fe^{+3}$ to its strong uniaxial anisotropy. The substitution of nonmagnetic $Ti^{+4}$ and magnetically weak $Co+^2ion for Fe^{+3}$ sublattices reduces the uniaxial anisotropy and those compounds open a new application field of noise suppressor at high frequencies. In this study, the magnetic and microwave absorbing properties are investigated in Ti-and Co-substituted barium ferrites ($BaFe_{12-2X} Ti_XCo_XO_{19}$). The saturated magnetization decreases linearly with the substitution of Ti and Co. The rapid drop in coercive force is observed with Ti and Co substitution upto x=1.2. The magnetic permeability spectrum shows the natural magnetic resonance in the specimens with small coercive force and large attenuation of microwave is predicted in those specimens at high frequencies (above 4 GHz).

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Effects of $SiO_2$ and Seed on Ba-ferrite Synthesized by Molten Salt (용융염법으로 합성한 Ba-ferrite의 $SiO_2$ 및 Seed 첨가 효과)

  • 김영근;이승관;김현식;오영우
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • pp.326-329
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    • 1996
  • In order to synthesize Ba-ferrite fine particles by molten salt method and inhibit the abnormal grain growth of sintered specimen, KCI anti NaCl were added to basic composition to 50% by weight, and added 1 male% of $SiO_2$ to control the shape of Ba-ferrite particles. $H_{c}$ and $M_{r}$ were decreased when F $e^{3+}$ was substituted with $Co_{2+}$ and $Ti_{4+}$ from x=0 to x=1.0 in $BaFe_{12-2x}$ $Ti_{x}$ $Co_{x}$ $O_{19}$ , and 1 mole% $SiO_2$ increased the size but shortened c-axis of hexagonal ferrite. Seeds added in Ba-ferrite particle effected inhibition of abnormal grain growth during sintering.ing.g.

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Mossbauer Studies of the $H_2$ Reduction Effects On Magnetic Properties of Sr-Ba Substituted Hexgonal Ferrite (치환형 Sr-Ba 육방 페라이트들의 자기적 성질에 수소환원이 미치는 효과에 관한 Mossbauer 분광학적 연구)

  • 박재윤;권명회;이재광
    • Journal of the Korean Magnetics Society
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    • v.9 no.1
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    • pp.35-40
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    • 1999
  • Sr substituted materials for some barium in M-type barium ferrite powder and Co-Ti substituted Sr-Ba hexagonal ferrite powder were prepared by citrate sol-gel method and 2 MOE sol-gel method these hexaferrite particles were reduced for 1hr in the hydrogen gas. The reduction temperatures were varied in the range of 250 $^{\circ}C$ to 500 $^{\circ}C$. X-ray diffraction patterns were measured using diffractometer with Cu $K_{\Alhpa}$ radiation. Mossbauer absorption spectra were measured with a constant acceleration spectrometer. We have focused on studying the origin of increasing $M_s$ by M$\"{o}$ssbauer spectroscopy. Ferrite particles which were sintered at 105$0^{\circ}C$ were found to be typical magnetoplumbite structure and single phase. XRD patterns with varying the reduction temperatures in $Sr_{0.5}Ba_{0.5}Fe_{10}O_{19}$ indicates ferrites particles become composite hexaferrites containing $\alpha$-Fe at T_{red}=350 \;$^{\circ}C$$. On the otherhand, it was found that $Co^{2+}$ ions and $Ti^{4+}$ ions in $Sr_{0.7}Ba_{0.3}Fe_{10}CoTiO_{19}$ prevent from changing $Fe^{3+}$ ions to $\alpha$-Fe during the $H_2$ reduction. Comparing Mossbauer results with XRD results, we have determined most of $\alpha$-Fe are reduced from $4f_{vi}$ sites and 12k sites of $Fe^{3+}$ ions. These $\alpha$-Fe phase bring the induced anisotropy and increase saturation magnetization $M_s$.TEX>.

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Magnetic and Microwave Absorbing Properties of M-type Ba-ferrite($BaFe_{12-2X}Ti_XCo_XO_{19}$)with Planar Magnetic Anisortropy (면내 자기이방성을 갖는 M-type Ba-ferrite($BaFe_{12-2X}Ti_XCo_XO_{19}$)의 자기적특성 및 전파흡수특성)

  • 조한신;김성수
    • Journal of the Korean Institute of Resources Recycling
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    • v.7 no.4
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    • pp.22-26
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    • 1998
  • The purpose of this experimenL is to investigate the magnetic anisotropy and microwave absorbing properties in M-type Bat territe (${BaFe}_{12-2X}{A}_{X}{Me}_{X}{O}_{19}$), where $Fe_{3+}$ is substituted by $Ti_{4+}$ in A site and $Co_{2+}$ in Me site. The saturation magnetization (Ms) is linearly decreased with the substitution rate(x) and the coerciviLy (He) is rapidly decreased in accordance with the reduction in t the magnetocrystalline anisotropy For the specimen with x=0.8 and thickness of 2 mm, the reflection loss calculated from the n material constants is less than -10 dB (90% absorption) in the frequency range of 10~16 GHz. The absorption loss is pre이.ctcd t to be more than 20 dElern in the frequency range of 12-16 GHz. The results demonstrate that the Ti-Co substituted M-type Ba-ferrite can be effectively used as a microwave absorber at high frequency range.

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Preparation and Oxygen Permeability of Tubular $Ba_{0.5}Sr_{0.5}Co_{0.8}Fe_{0.2}O_{3-{\delta}}$ Membranes with $La_{0.6}Sr_{0.4}Ti_{0.3}Fe_{0.7}O_{3-{\delta}}$ Porous Coating Layer (다공성의 $La_{0.6}Sr_{0.4}Ti_{0.3}Fe_{0.7}O_{3-{\delta}}$가 코팅된 $Ba_{0.5}Sr_{0.5}Co_{0.8}Fe_{0.2}O_{3-{\delta}}$ 관형 분리막의 제조 및 투과 특성)

  • Kim, Jong-Pyo;Pyo, Dae-Woong;Park, Jung-Hoon;Lee, Yong-Taek
    • Membrane Journal
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    • v.22 no.1
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    • pp.8-15
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    • 2012
  • Tubular $Ba_{0.5}Sr_{0.5}Co_{0.8}Fe_{0.2}O_{3-{\delta}}$ membranes with $La_{0.6}Sr_{0.4}Ti_{0.3}Fe_{0.7}O_{3-{\delta}}$ porous coating layer were prepared by extrusion and dip coating technique. XRD and SEM result showed the tubular membrane possessed the perovskite structure and porouscoating layer (thickness= about $2{\mu}m$) in surface. The oxygen permeation test was measured at condition of ambient air (feed side) and vacuum (permeate side) in the temperature range from 750 to $950^{\circ}C$. The oxygen permeation flux of $Ba_{0.5}Sr_{0.5}Co_{0.8}Fe_{0.2}O_{3-{\delta}}$ tubular membrane with $La_{0.6}Sr_{0.4}Ti_{0.3}Fe_{0.7}O_{3-{\delta}}$ porous coating layer reached maximum $3.2mL/min{\cdot}cm^2$ at $950^{\circ}C$ and was higher than non-coated $Ba_{0.5}Sr_{0.5}Co_{0.8}Fe_{0.2}O_{3-{\delta}}$ tubular membrane. Long-term stability test result indicated that the oxygen permeation flux was quite stable during the 11 day.

The Effect of Hydrogen Reduction Treatment on Properties of Ba-ferrite (환원처리가 Ba-ferrite의 물성에 미치는 영향)

  • 홍양기;정홍식;김현준
    • Journal of the Korean Magnetics Society
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    • v.7 no.1
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    • pp.25-30
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    • 1997
  • Physical and magnetic behaviors of reduced Co-Zn-Ti-Sn substituted Ba-ferrite particles with hydrogen are different from those of reduced-pure Ba-ferrite particles. The coercivity of substituted Ba-feffite particles shows a peaking effect with the reduction temperature ranging from 250 to 520 $^{\circ}C$, while the coercivity of pure Ba-ferrite decreases monotonically. The reduction process of substituted Ba-ferrite has been found to be devided into three steps. At the first and second steps, the magneto-plumbite structure maintained. When the reduced-substituted Ba-ferrite particles are reoxidized, the coercivity is reversible at the first step but irreversible at the second step. During the third step of reduction process above 410 $^{\circ}C$. The magneto plumbite structure was collapsed with formation of $\alpha$-Fe and $BaFeO_{3-x}$ phases and consequently the coercivity distribution is broaden and the coercivity irreversible. The coercivity and saturation magnetization decreases and increases up to 130 emu/g respectively. In this study, it is found that the substituted elements prevent the magneto-plumbite structure from collapse during the reduction process and furthermore migrate from the magnetic sites of $2a+4f_{IV}$, 2b, and 12k to $4f_{VI}$ and 12k'. An increase in the coercivity before the collapse of magneto-plumbite structure is attributed to the migration of cations in hexagonal Ba-ferrite structure.

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