• Journal of Magnetics
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• v.22 no.2
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• pp.169-174
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• 2017

In this work, lithium ferrite ($Li_{0.5}Fe_{2.5}O_4$) nanoparticles were prepared via mechanochemical processing and subsequent heat treatment at a relatively low ($600^{\circ}C$) calcining temperature. The raw materials used were high purity $Fe_2O_3$ and $Li_2CO_3$ that were milled for between 2 and 20 h. The milled powders were then calcined at temperatures of 500 and $600^{\circ}C$ for 5 h in air. XRD results show that optimum conditions to obtain single phase lithium ferrite nanoparticles with a mean crystallite size of about 23 nm, using Scherrer's formula, are 10 h milling and calcination at $600^{\circ}C$. Saturation magnetization and coercivity of the single phase Li ferrite nanoparticles are 44.6 emu/g and 100 Oe respectively, which are both smaller than those of the bulk Li ferrite. The Curie temperature of the single sample was determined by a Faraday balance, which is $578^{\circ}C$ and smaller than that of bulk Li ferrite.

• Journal of Electrochemical Science and Technology
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• v.12 no.2
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• pp.285-295
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• 2021

The inverse spinel Cobalt ferrite (CoFe₂O₄, CFO) is considered to be a promising alternative to commercial graphite anodes for lithium ion batteries (LIBs). However, the further development of CFO is limited by its unstable structure during battery cycling and low electrical conductivity. In an effort to address the challenge, we construct three-dimensional hierarchical flower-like CFO nanoclusters (CFO NCs)-decorated carbonized cotton carbon fiber (CFO NCs/CCF) composite. This structure is consisted of microfibers and nanoflower cluster composited of CFO nanoparticle, in which CCF can be used as a long-range conductive matrix, while flower-like CFO NCs can provide abundant active sites, large electrode/electrolyte interface, short lithium ion diffusion path, and alleviated structural stress. As anode materials in LIBs, the flower-like CFO NCs/CCF exhibits excellent electrochemical performance. After 100 cycles at a current density of 0.3 A g^-1, the CFO NCs/CCF delivers a discharge/charge capacity of 1008/990 mAh g^-1. Even at a high current density of 15 A g^-1, it still maintains a charge/discharge capacity of 362/361 mAh g^-1.

• Korean Journal of Materials Research
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• v.14 no.9
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• pp.655-658
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• 2004

Lithium ferrites are a low-cost material which have been prominent in the high frequency core industry because of their excellent temperature performance and high squareness ratio. In order to develope the lithium ferrites with the high squareness and low coercive force, the ferrites of $Li_{0.48}Bi_{0.02}Ni_{0.04}Fe_{2.46-x}O_4$ were investigated the by varying composition, temperature and frequency. Electric loss of the Li-ferrite was lowered with the substitution of $Mn_{2}O_3$. The addition of $Mn_{2}O_3$ increased the magnetic induction (Bm&Br) but decreased the coercive force (Hc) and the squareness ratio (R=Br/Bm). Also, the Br value was stable at environmental temperature variation.

• Journal of the Korean Magnetics Society
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• v.9 no.5
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• pp.234-238
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• 1999

Lithium ferrites are prominent in the element of microwave frequency communication core and high frequency memory core because of their low coercivity and the high squareness ratio. This paper reports primarily the development of lithium ferrites with the low coercivity and high squareness ratio. The materials with $Li_{0.48-0.5x}Bi_{0.02}Ni_{0.04}Zn_xFe_{2.46-0.5x}O_4$ (x = 0,0.01, 0.02, 0.03) have been prepared to investigate the physical properties. The addition of ZnO gave raised maximum induction $(B_m)$ and decreased coercive force $(H_c)$, but the squareness ratio $(R\;=\;B_m/B_r)$ was decreased. The specimen of squareness ratio R=0.82, coercive force $H_c=\;1.80\;Oe$ was obtained for $Li_{0.48-0.5x}Bi_{0.02}Ni_{0.04}Zn_xFe_{2.46-0.5x}O_4$ (X=0) sintered at 105$0^{\circ}C$. Also the sample of squareness ratio R = 0.75, coercive force $H_c=\;1.70\;Oe$ for $Li_{0.48-0.5x}Bi_{0.02}Ni_{0.04}Zn_xFe_{2.46-0.5x}O_4$ (X = 0) sintered at 110$0^{\circ}C$ was measured. The Tc was obtained 463$^{\circ}C$ and the Br of environmental temperature variation was stable.

• Journal of Radiation Protection and Research
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• v.14 no.2
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• pp.37-44
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• 1989

An improved water chemistry technique was studied to reduce radioactivity build-up in reactor coolant system. The technique is convering the current coordinated lithium-boron chemistry regime to the elevated lithium chemistry regime in order to maintain high pH. Correlations between reactor coolant pH and radioactivity build-up were analized by using pH data from domestic PWRs. Consequently, it was founded that high pH chemistry was moer effective for radioactivity build-up reduction than current chemistry regime. This fact had revealed that much portion of reactor coolant corrosion products were nickel ferrite rather than magnetite, and that pH value ranging 7.0-7.4 was appropriate for high-pH chemistry operation.

• Journal of the Korean Ceramic Society
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• v.16 no.1
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• pp.26-30
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• 1979

The microstructures and memory core characteristics of substituted lithium ferrites with addition of $Bi_2O_3$, $V_2O_5$, $Nb_2O_3$, and $P_2O_5$ were investigated. The effects of composite flux on the sintering of the substituted lithium ferrites were also studied. The results show that the addition of $Bi_2O_3$, $V_2O_5$, and $Nb_2O_5$ enhances sintering whereas $Sb_2O_3$ and $P_2O_5$ inhibits it, and that the addition of $Nb_2O_5$ results in uniform grain size while the addition of $Bi_2O_3$ or $V_2O_5$ results in non-uniformity in grain size. When $P_2O_5$ was added with $V_2O_5$ or $Bi_2O_3$, however, it results in uniform grain size and improved memory core properties.

• Journal of Magnetics
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• v.15 no.1
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• pp.25-28
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• 2010

This study examined the crystallographic and magnetic properties of vanadium-substituted lithium cobalt titanium ferrite, $Li_{0.7}Co_{0.2}Ti_{0.2}V_{0.2}Fe_{1.7}O_4$. Ferrite was synthesized using a conventional ceramic method. The samples annealed below $1040^{\circ}C$ showed X-ray diffraction peaks for spinel and other phases. However, the sample annealed above $1040^{\circ}C$ showed a single spinel phase. The lattice constant of the sample was $8.351\;{\AA}$, which was relatively unaffected by vanadium-substitution. The average grain size after vanadium-substitution was $13.90\;{\mu}m$, as determined by scanning electron microscopy. The M$\ddot{o}$ssbauer spectrum could be fitted to two Zeeman sextets, which is the typical spinel ferrite spectra of $Fe^{3+}$ with A and B sites, and one doublet. From the absorption area ratio of the M$\ddot{o}$ssbauer spectrum, the cation distribution was found to be ($Co_{0.2}V_{0.2}Fe_{0.6})[Li_{0.7}Ti_{0.2}Fe_{1.1}]O_4$. Vibrating sample magnetometry revealed a saturation magnetization and coercivity of 36.9 emu/g and 88.6 Oe, respectively, which were decreased by vanadium-substitution.

• Journal of the Korean Ceramic Society
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• v.19 no.4
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• pp.267-274
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• 1982

The sintering behavior and B-H loop properties of $Li_{0.5O4}$ with the addition of $Nb_2O_5$ and $V_2O_5$ have been investigated by observation of microstructures and measurement of semi-static hysteresis loops. The sintering temperature was lowered by the additions of $Nb_2O_5$ and $V_2O_5$ and the effect of $V_2O_5$ addition was greater than that of $Nb_2O_5$. The abnormal grain growth was observed at about 100$0^{\circ}C$(d:4.6g/㎤) and 85$0^{\circ}C$(d:4.5g/㎤) in the specimens with the addition of $Nb_2O_5$ and $V_2O_5$ respectively. The addition of $Nb_2O_5$ retulted in a large and uniform grain size, and the addition of $V_2O_5$ resulted in a uniform grain size but the final density was lower than that of the pure specimen. The squareness was increased and the coercive force was decreased by the addition of $Nb_2O_5$, and the squareness was decreased and the coercive force was increased by the addition of $V_2O_5$. These effects could be explained by a large and uniform grain size, and by a lower final density of specimens with the addition of $Nb_2O_5$ and $V_2O_5$ respectively.

• Proceedings of the IEEK Conference
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• 2001.10a
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• pp.106-110
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• 2001

Formation of stoichiometric lithium-, nickel-, and zinc- ferrites by calcining organo-metallic precursors a temperature below 40$0^{\circ}C$ is examined using DTA/TG, and XRD techniques. It attempts to simulate th immobilization of metal ions in industrial liquid influents (waste) through the synthesis of stoichiometric spinel ferrites (SSF). Two steps of the SSF formation during thermal treatments are noted. The transformation of magnetite to ${\gamma}$ - Fe$_2$O$_3$and subsequent first formation of SSF were observed at temperatures ranging from 200 to 45$0^{\circ}C$. Th formation of cation-containing ${\gamma}$-Fe$_2$O$_3$and subsequent second formation of the ferrite occurred at temperature ranges of < 45$0^{\circ}C$ and 500 to $650^{\circ}C$, depending on the heating rate used. Then the temperature range of 200t 45$0^{\circ}C$ is critical to the performance of the technique, because a calcination at the range would lead to a complete formation of SSF, avoiding the occurrences of ${\gamma}$-Fe$_2$O$_3$and ion-containing ${\gamma}$-Fe$_2$O$_3$. If not, so $\alpha$-Fe$_2$O$_3$would occur. And annealing at temperature above $650^{\circ}C$ must be employed by which solid-state reactio of $\alpha$-Fe$_2$O$_3$with metal ions (possibly metal oxides) to form SSF can be conducted.

• Korean Journal of Materials Research
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• v.28 no.9
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• pp.489-494
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• 2018

Lead free $(1-x)(0.675BiFeO_3-0.325BaTiO_3)-xLiTaO_3$ (BFBTLT, x = 0, 0.01, 0.02, and 0.03, with 0.6 mol% $MnO_2$ and 0.4 mol% CuO) were prepared by a solid state reaction method, followed by air quenching and their crystalline phase, morphology, dielectric, ferroelectric and piezoelectric properties were explored. An X-ray diffraction study indicates that lithium (Li) and tantalum (Ta) were fully incorporated in the BFBT materials with the absence of any secondary phases. Dense ceramic samples (> 92 %) with a wide range of grain sizes from $3.70{\mu}m$ to $1.82{\mu}m$ were obtained in the selected compositions ($0{\leq}x{\leq}0.03$) of BFBTLT system. The maximum temperatures ($T_{max}$) were mostly higher than $420^{\circ}C$ in the studied composition range. The maximum values of maximum polarization ($P_{max}{\approx}31.01{\mu}C/cm^2$), remnant polarization ($P_{rem}{\approx}22.82{\mu}C/cm^2$) and static piezoelectric constant ($d_{33}{\approx}145pC/N$) were obtained at BFBT-0.01LT composition with 0.6 mol% $MnO_2$ and 0.4 mol% CuO. This study demonstrates that the high $T_{max}$ and $d_{33}$ for BFBTLT ceramics are favorable for industrial applications.