• Journal of the Korean Magnetics Society
• /
• v.9 no.1
• /
• pp.17-22
• /
• 1999

Hexagonal M-type barium ferrite $BaFe_{12}O_{19}$ was prepared by a direct solid state reaction between $BaCO_3$ and ${\Alpha}-Fe_2O_3$ powders at temperatures ranging from 800 to 1000 $^{\circ}C$ in a nitrogen or air environment. The effects of NaCl on phase transformation of mixture of $BaCO_3$ and ${\Alpha}-Fe_2O_3$ to $BaFe_{12}O_{19}$ were studied using X-ray diffraction and M$\"{o}$ssbauer spectroscopy. Regardless of the environment for heat treatment or the added NaCl, two phases, BaFe and ${\Alpha}-Fe_2O_3$, coexist for samples heat treated at 800 $^{\circ}C$, but a single phase was observed from samples heat treated at 100$0^{\circ}C$ in both air and nitrogen environments. It was found that the addition of NaCl reduced the amount of $a-Fe_2O_3$ phase.hase.

• Journal of the Korean Magnetics Society
• /
• v.9 no.1
• /
• pp.35-40
• /
• 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>.

• Journal of the Korean Magnetics Society
• /
• v.19 no.6
• /
• pp.216-221
• /
• 2009

Y-type barium ferrite $Ba_2Co_2Fe_{12}O_{22}$ was synthesized by a solid state reaction method. Effects of metal ion mole ratio and calcination temperatures on magnetic properties and microstructures of the synthesized powders were investigated. Phase analysis and microstructure observation were performed with a XRD (X-ray diffractometer) and a FESEM (field effect scanning electron microscope), respectively. Magnetic properties of the powders were measured with a VSM (vibrating sample magnetometer). Single phase Y-type was synthesized when metal ion mole fraction $Fe^{3+}:\;Ba^{2+}:\;Co^{2+}$ was 6 : 1 : 1 and calcination temperature was $1050\;{^{\circ}C}$. High saturation magnetization value of 39.1 emu/g was obtained when metal ion mole fraction $Fe^{3+}:\;Ba^{2+}:\;Co^{2+}$ was 8 : 1 : 1 and calcination temperature was $1200\;{^{\circ}C}$.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.34 no.5
• /
• pp.386-392
• /
• 2021

Multiferroics exhibiting the coexistence and a possible coupling of ferromagnetic and ferroelectric order are attracting widespread interest in terms of academic interests and possible applications. However, room-temperature single-phase multiferroics with soft ferromagnetic and displacive ferroelectric properties are still rare owing to the contradiction in the origin of ferromagnetism and ferroelectricity. In this study, we demonstrated that sizable ferromagnetic properties are induced in the ferroelectric bismuth ferrite-barium titanate system simply by introducing Co ions into the A-site. It is noted that all modified compositions exhibit well-saturated magnetic hysteresis loops at room temperature. Especially, 70Bi_0.95Co_0.05FeO₃-30Ba_0.95Co_0.05TiO₃ manifests noticeable ferroelectric and ferromagnetic properties; the spontaneous polarization and the saturation magnetization are 42 µC/cm² and 3.6 emu/g, respectively. We expect that our methodology will be widely used in the development of perovskite-structured multiferroic oxides.

• Composites Research
• /
• v.21 no.2
• /
• pp.31-35
• /
• 2008

In order to design light weight and high efficient electromagnetic wave absorbing materials, hollow magnetic particles have been introduced in this study. The electroless plating method has been utilized to coat Ni and Fe on the substrates of synthesized polystyrene particles of submicron size. Removing polystyrene particles by heat treatment resulted in hollow structures. Observation by SEM, TEM and EDS confirmed the surface morphology and coating thickness of Ni and Fe. Polymeric composites containing hollow particles were tested in order to compare the electromagnetic properties between Ni coated and Fe costed particles. The composite of 30 wt% Fe hollow particles showed the higher complex permeability than Ni hollow particles or the conventional barium ferrite particles.

• Korean Journal of Materials Research
• /
• v.8 no.8
• /
• pp.775-779
• /
• 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.

• Resources Recycling
• /
• v.7 no.4
• /
• pp.22-26
• /
• 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.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.12 no.11
• /
• pp.5357-5364
• /
• 2011

The objective of this study is development of carbon recycle technology which convert carbon dioxide captured from flue gas to carbon monoxide or carbon and reuse in industrial fields. Since carbon dioxide is very stable and difficult to decompose, metal oxide was used as activation agent for the decomposition of carbon dioxide at low temperature. Metal oxides which convert $CO_2$ to CO or carbon were prepared using Ba-ferrite by solid and hydrothermal synthesis. TPR/TPO and TGA were used in this study. The results of TPR by H2 and TPO by $CO_2$ showed that Ba-ferrite powders synthesized by hydrothermal method were better than those by solid method. TGA showed contrary results that reduction of Ba-ferrite powders synthesized using solid method by $H_2$ was 21.96 wt%, oxidation by $CO_2$ was 21.24 wt% and 96.72 wt% of $CO_2$ decomposition efficiency showing excellent oxidation-reduction characteristics at $500^{\circ}C$.

• Korean Journal of Materials Research
• /
• v.7 no.5
• /
• pp.423-430
• /
• 1997

졸-겔 dip coating법에 의해 제조한 바륨페라이트 박막의 미세구조와 결정학적인 구조 특성에 관해 조사하였다. 기판에 형성된 바륨페라이트 입자는 침상 형태의 입자들로 구성되어 있었으며, C축은 장축 방향이었고, 막 두께가 증가함에 따라 침상형 입자들은 기판에 평행하게 배향하는 경향을 나타내었다. 박막은 바륨페라이트층, Ba, Fe, SiO$_{2}$로 구성되어 있는 중간층, 그리고 기판층인 SiO$_{2}$층으로 구성되어 있었으며, 중간층과 SiO$_{2}$층간의 계면은 Ba 와 SiO$_{2}$간의 화합물로 구성되어 있었다. 침상 형태의 입자는 95$0^{\circ}C$에서 3시간 열처리하므로써 완전히 소실하였고, 130$0^{\circ}C$에서 3시간 열처리하므로써 c면이 기판에 평행하게 위치하는 완전한 육각판상 형태의 입자로 변화되었다.

• Journal of the Korean Magnetics Society
• /
• v.24 no.1
• /
• pp.1-10
• /
• 2014

$Co_2Z$-type barium ferrites ($Ba_3Co_2Fe_{24}O_{41}$) were synthesized using variation method. First, M-type, $Co_2Y$-type and $Co_2Z$-type synthesized by hydrothermal method. Second, M- and Y-type precursors for synthesis of $Co_2Z$ hexaferrite by hydrothermal and ball milling method. the morphology, structure and magnetic properties of the barium ferrite particles were characterized using XRD, FESEM, VSM, impedance. As a result, Single phase of M-type and $Co_2Y$-type were obtained. Manufactured powders of M+Y ball milling, M+Y hydrothermal were similar to single phase of $Co_2Z$-type hexaferrite, all powders were obtained theoretical magnetization (50 emu/g). The largest initial permeability were obtained $Co_2Z$ hexaferrite synthesized by reagent precusor, With increasing calcination temperature was lowered the initial permeability. In another synthesis didn't almost that little change could be found.