• Journal of Magnetics
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• 제15권1호
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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.

• 한국재료학회지
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• 제27권8호
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• pp.416-421
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• 2017

V-substituted $SrTiO_3$ thermoelectric oxide materials were fabricated by the conventional solid state reaction method. From X-ray diffraction pattern analysis, it can be clearly seen that almost every vanadium atom incorporated into the $SrTiO_3$ provided charge carriers. The electrical conductivity ${\sigma}$, Seebeck coefficient S, and thermal conductivity k were investigated in a high temperature regime above 1000 K. The addition of vanadium significantly reduced the thermal conductivity and enhanced the Seebeck coefficient, as well as the electrical conductivity, thus enhancing the ZT value. A maximum ZT value of 0.084 at 673 K was observed for the sample with 1.0 mole% of vanadium substitution. In this study, the reason for the enhanced thermoelectric properties via vanadium addition was also investigated.

• 공업화학
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• 제5권2호
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• pp.361-372
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• 1994

수열합성법 및 탈알루미늄 처리 이후 $NH_4VO_3$담지법으로 바나듐이 함유된 MFI형 제올라이트를 제조하였다. X선 회절분석, 시차 열분석, 적외선 분광분석 및 전자스핀공명분석을 수행하여 바나듐의 격자구조 내로의 도입을 검토하였다. 탈알루미늄된 ZSM-5에 $NH_4VO_3$를 담지시키고 소성한 경우에도 수열합성법으로 제조한 시료와 같이 바나듐이 구조 내로 도입될 수 있었다. 제올라이트 구조 중의 바나듐은 고온처리에 의해 산화-환원과정을 거칠 수 있으며, 이들은 원자단위로 분산되어 고정됨을 나타내었다. 벤젠 수산화반응과 hexane 및 알코올의 산화반응을 바나듐 함유 MFI형 제올라이트의 특성 검토를 위한 시험반응으로 이용하였다.

• 분석과학
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• 제5권2호
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• pp.203-211
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• 1992

Ni-36.5at.%Al 합금에서 결정립계에서의 scavenging 원소로 알려진 V를 첨가하여 이 합금의 파괴거동 및 마르텐사이트 미세조직에 미치는 V의 영향에 대해 조사하였다. 시편의 파단면은 주사전자현미경으로 관찰하였고 EDX spectrometer를 사용하여 파단면의 조성을 분석하였으며 투과전자현미경으로 마르텐사이트 내부조직의 변화에 대해 조사하였다. V의 첨가로 입계파괴에서 입내파괴로 파괴 모드의 변화를 나타내었으며 EDX spectrometer로 분석한 결과 입내에 비해 입계에 Al의 함량이 상대적으로 증가되는 양상을 보여 주었다. Ni-36.5at.%Al 합금의 경우 마르텐사이트 플레이트는 내부쌍정으로 이루어져 있으나 V의 첨가에 따라 twinned 마르텐사이트 조직은 사라지며 stacking fault와 고밀도의 전위를 가진 modulated 조직이 점차 지배적으로 형성되는 것이 관찰되었다. Stacking fault를 분석한 결과 Al과 V의 치환에 따른 extrinsic fault였으며 high-energy 상태인 이 stacking fault가 있는 부위에 유해 원소인 S가 편석됨으로써 결정립계에서의 파괴를 줄일 수 있었다.

• 한국결정성장학회지
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• 제7권3호
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• pp.437-448
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• 1997

직접 수열합성법과 변조된 처리법을 이용하여 세공경이 큰 제올라이트의 결정구조내에 바나듐원자가 치환되도록 하였다. 제올라이트 골격에 바나듐이 도입되었는지의 여부를 기기분석을 통하여 시험하였다. X선회절분석의 결과, 바나듐이 제율라이트의 구조중에 도입되면 결정골격중의 실리콘원자 대신 치환되어 결정단위세포의 확장을 나타내었다. 또한 FTIR, UV-Vis 및 Si-MAS-NMR 스펙트럼결과는 제올라이트 골격내로의 바나듐의 도입을 강하게 됫받침하였다. 제올라이트중의 알루미늄을 산처리로 용출시키면, 격자에 빈자리를 제공하여 2차수열처리법에 의한 바나듐의 도입을 가능케 하였다.

• 한국결정성장학회지
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• 제8권1호
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• pp.160-168
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• 1998

치환에 의한 wagnerite의 색상변화 및 고용체 형성한계를 살펴보기 위해 wagnerite ($A_2XO_4Z$)를 합성한후 각 구성원소들을 치환하였다. Ca-wagnerite의 Ca 대신에 Mg, Co, Ni, Cu로 치환하여 용해도가 한정된 고용체를 얻었다. 이들 중 (Mg,Ca)-wagnerite와 (Co,Ca)-wagnerite의 경우에만 단일상의 wagnerite를 합성하였으며 이들의 색상은 각각 백색과 자주색이었다. 그 외의 조성 및 (Ni,Ca)-wagnerite와 (Cu,Ca)-wagnerite의 경우에는 여러상이 혼재해 있는 것으로 나타났다. $A^{5+}$자리에 Li을 치환해 보았으며 또한 $X^{5+}$대신 V을 치환하여 진한 자주 및 금색, 옅은 노란색의 wagnerite를 합성하였으며, Z- 대신 Cl을 치환한 경우 단일상의 wagnerite을 얻지 못하였다.

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2007년도 The 1st International Symposium on Advanced Magnetic Materials
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• pp.52.2-52.2
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• 2007

• Applied Microscopy
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• 제47권3호
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• pp.105-109
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• 2017

The effect of temperature and vanadium metal concentration on the electronic and thermoelectric properties of Si in the diamond cubic structure has been investigated using a combination of density functional theory simulations and the semi classical Boltzmann's theory. The BotzTrap code within the constant relaxation time approximation has been used to obtain the Seebeck coefficient and other transport properties of interest for alloys of the structure $Si_{1-x}V_x$, where x is 0, 0.125, 0.25, 0.375, and 0.5. The thermoelectric properties have been extracted for a temperature range of 300 K to 1,000 K. The general trend with V atom substitution for Si causes the Seeback coefficient to increase and the thermal conductivity to decrease for the various alloys. The optimum values are for $Si_5V_3$ and $Si_4V_4$ alloys for charge carrier concentrations of $10^{21}cm^{-3}$ in the mid temperature range of 500~800 K. This is a very desirable effect for a promising thermoelectric and the figure of merit ZT approaches 0.2 at 600 K for the p-type $Si_5V_3$ alloy.

• 한국재료학회지
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• 제11권11호
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• pp.960-964
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• 2001

$Bi_{3.99}Ti_{2.97}V_{0.03}O_{12}$ (BTV) thin films with 3 mol% vanadium doping were Prepared on $Pt/Ti/SiO_2/Si$ substrate by sol-gel method. X-ray diffraction analysis indicated that single-phase layered perovskite were obtained and preferred orientation was not observed. Under the annealing temperature at $600^{\circ}C$, the surface morphology of the BTV thin films had fine-rounded particles and then changed plate-like at $650^{\circ}C$ and $700^{\circ}C$. The remanent polarization $(2P_r)$ and coercive field $(2E_c)$ of $700^{\circ}C$ annealed BTV thin film were 25 $\mu$C/cm$^2$ and 116 kV/cm, respectively. In addition, BTV thin film showed little polarization fatigue during $10_9$ switching cycles. These improved ferroelectric properties were attributed to the increased rattling space and reduced oxygen vacancies by substitution $Ti^{4+}$ ion (68 pm) with smaller $V^{5+}$ ion (59 pm). The dielectric constant and loss were measured 130 and 0.03 at 10 kHz, respectively.

• 자원환경지질
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• 제30권1호
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• pp.35-49
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• 1997

The coal formation of the Deokpyeong area are interbedded along metapelites of the Ogcheon Supergroup, which are composed mainly of graphite, quartz, muscovite and associated with small amounts of biotite, chlorite, pyrite and barite. The ratios of $SiO_2/Al_2O_3$, $Al_2O_3/Na_2O$ and $K_2O/Na_2O$ of the coaly metapelite are variable and wide range from 1.80 to 10.21, from 27.8 to 388.8 and from 7.6 to 61.8, respectively. These coal formation were deposited in basin of marine environments, and the REE of these rocks are not influenced with metamorphism and hydrothermal alterations on the basis of $Al_2O_3$ versus La, La against Ce, the ratios of La/Ce (0.19 to 0.99) and Th/U (0.02 to 4.75). These rocks also show much variation in $La_N/Yb_N$ (1.19 to 22.89), Th/Yb (0.14 to 21.43) and La/Th (0.44 to 13.67), and their origin is explained by derivation from a mixture of sedimentary and igneous rocks. The wide range in trace and REE element characteristics as Co/Th (0.12 to 2.78), La/Sc (0.33 to 10.18), Sc/Th (0.57 to 5.73), V/Ni (8 to 2347), Cr/V (0.02 to 0.67) and Ni/Co (1.56 to 32.95) of these coaly metapelites argues for inefficient mixing of the various source lithologies during sedimentation. Deep to pale green barium-vanadium muscovites (vanadium-oellacherite) have been found in this coal formations. Modes of occurrence and grain size of muscovite are heterogeneous, but most of the barium and vanadium-bearing muscovites occur along the boundaries between graphite and quartz grains, ranging from 200 to $350{\mu}m$ in length and from 40 to $60{\mu}m$ in width. Results of X-ray diffraction data of the minerals characterized to be monoclinic system with $a=5.249{\AA}$, $b=8.939{\AA}$, $c=20.924{\AA}$ and ${\beta}=95.894^{\circ}$. Representative chemical formula of the muscovite was $(Na_{0.09}K_{1.44}Ba_{0.46})(Al_{2.75}Ti_{0.07}V_{0.56}Fe_{0.08}Mg_{0.50})(Si_{6.12}Al_{1.88})O_{22}$. The V possibly substitute octahedral Al, and the Ba is coupled substitution of $K^+Si^{4+}=Ba^{2+}Na^+Ca^{2+}$, which compositional ranges of V and Ba are from 0.42 to 0.69 and from 0.34 to 0.56 based on $O_{22}$, respectively. Formation mechanism of the barium-vanadium muscovites in the coaly metapelite is shown that the formed by high pressure and temperature from regional metamorphism origanated during diagenesis at the interface between a basinal brine and organic matter.