• 한국세라믹학회지
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• 제37권1호
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• pp.12-20
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• 2000

Dielectric property of Ba-modified 0.65Pb(Mg1/3Nb2/3)O3-0.35PbTiO3 ceramics having compositions near the morphotropic phase boundary was investigated. For the specimens having Ba contents between 0 and 20 at%, the average transition temperature was decreased linearly with increasing Ba contents and the degree of hysteresis was also decreased with increasing Ba contents. The maximum dielectric constants (K), electric field induced polarization(P) and electrically-induced strain(S) were found to exihibit a maximum value at∼3 at% of Ba. The increase of S and the decrease of hysteresis by minor additions of Ba impurities indicated the development of new higher perfomance actuator materials. The composition of Ba-PMN-PT (10/65/35) may be appropriate for capacitor materials because of low hysteresis and high polarization.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2001년도 추계 학술발표강연 및 논문개요집
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• pp.129-129
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• 2001

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 하계학술대회 논문집
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• pp.374-374
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• 2009

We have fabricated pure YBCO films and $BaZrO_3$ doped ones on $CeO_2$ buffered YSZ single crystal substrates using rf-sputtering method. In this work, pure YBCO and 2 vol% BZO doped YBCO target were used to investigate the flux pinning properties of BZO doped YBCO films compared to undoped ones. BZO nanodots within the superconducting materials was known to comprise the self-assembled columnar defects along the c-axis from the bottom of YBCO films up to the top surface, thus can be a very strong pinning sites in the applied magnetic field parallel to them. We will discuss the possibility of growing self-assembled columnar defects in the rf-sputtering method. It is speculated that BZO and YBCO phases can separate and BZO form nanodots surrounded by YBCO epitaxial layers and continuous phase separation and ordering between these two materials, which was well studied in Pulsed Laser Deposition method. For this purpose, some severe experimental conditions such as on-axis sputtering, shorter target-substrate distance, high rf-power, etc was adopted and their results will be presented.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 춘계학술대회 논문집 유기절연재료 전자세라믹 방전플라즈마 일렉트렛트 및 응용기술
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• pp.79-82
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• 2002

$(Ba_{0.6-x}Sr_{0.4}Ca_x)TiO_3$ + ywt% MgO (x=0.10, 0.15, 0.20, y=0.0~3.0) ceramics were fabricated by the conventional solid-state reaction, and their structural and dielectric properties were investigated with variation of composition ratio and MgO doping content. A second phase, representative of MgO, appears in 3wt% MgO-doped BSCT specimens. Average grain sizes decreased with increasing amounts of MgO, and the BSCT(40/40/20) specimens doped with 3wt% MgO showed a value of $9.3{\mu}m$. The Curie temperature and relative dielectric constant at room temperature were decreased with increasing MgO doping content and Ca composition ratio. The relative dielectric constant was non-linearly decreased as the field strength is increased. The tunability was increased with decreasing a Ca content and the BSCT(50/40/10) specimen doped with 1.0wt% MgO content showed the highest value of 6.4% at 5kV/cm.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 추계학술대회 논문집 학회본부 C
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• pp.915-917
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• 1999

We investigated the effects of doping elements on the Bi system superconductor. The doping elements can be classified into two groups depending on their supeconducting characteristics in the Bi-Sr-Ca-Cu-O structure. The first group of doping elements(P and K) have a tendency to decompose the superconducting phase and reduce the optimal sintering temperature. The second group of doping elements(B, Si, Sn and Ba) almost uneffected the superconductivity of the 2223 and 2212 phase.

• 한국초전도ㆍ저온공학회논문지
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• 제17권4호
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• pp.30-33
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• 2015

We report the synthesis of Ni-doped $BaFe_2Se_3$ single crystals by using a flux method. X-ray diffraction (XRD) of $Ba(Fe_{1-x}Ni_x)_2Se_3$ shows a gradual peak shift with an increase in the nominal Ni-doping rate, x = 0, 0.05, and 0.10, due to a decrease in unit-cell volume. All samples show a spin glass transition, and temperature dependence of magnetic susceptibility shows a negligible change in the spin-glass transition temperature ($T_g$) with Ni concentration x. The temperature dependence of electrical resistivity for $BaFe_2Se_3$ shows an insulating behavior, and the resistivity value at 295 K and the activation energy ($E_a$) obtained from the Arrhenius plot decrease with increasing x. These results suggest that the Ni doping can be effectively worked as a dopant for electron charge carriers, but is less efficient in controlling the magnetic property, such as spin glass transition, in the $BaFe_2Se_3$ compound.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 하계학술대회 논문집 Vol.9
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• pp.55-55
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• 2008

이차전지의 음극 중 $LiC_6$는 높은 용량을 보이나 완충하는 프로세스 동안에 금속리튬에 가까운 potential을 갖게 되어 조작에 어려움이 있다. 이러한 대용물질로서 $Li_4Ti_5O_{12}$ spinel은 가볍고 높은 에너지 밀도를 가지고 있고 낮은 전압영역이 가능하여 이차전지의 음극 물질로서 유용하다. 그러나 $Li_4Ti_5O_{12}$ 물질 자체가 insulation이며, 고상합성법을 사용하게 되면 좋은 특성을 나타내기가 어렵다. 이번 실험에서는 고상합성을 통하여 $Ba^{2+}$와 $Sr^{2+}$이온을doping한 후 전기화학적 특성이 어떻게 향상되었는가를 연구하였다. Ba와 Sr을 첨가한 $Li_4Ti_5O_{12}$는 첨가하지 않은 물질에 비하여 보다 안정적인 평탄구역을 갖게 되었으며 방전용량이 $40mAhg^{-1}$의 향상을 가져왔다. 또한 Li half cell에서 100cycle 진행하는 동안 보다 안정적인 전극구조를 유지하였다.

• 한국재료학회지
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• 제13권12호
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• pp.846-849
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• 2003

Doping effect of various ions in Bi-layered ferroelectric $SrBi_2$$Nb_2$$O_{9}$ (SBN) ceramics was studied. Undoped SBN ceramic and SBN ceramics doped with $Ba^{2＋}$, $Pb^{2＋}$,$ Ca^{2＋}$ , $Bi^{3＋}$ , $La^{3＋}$ , $Ti^{4＋}$ , $Mo^{6＋}$ , and $W^{6＋}$ ions were made by a solid state reaction. Dielectric constants were measured with temperature. Ferroelectric transition temperature decreased with $Pb^{2＋}$ , $Ba^{2＋}$ , $La^{3＋}$ doping, but the transition temperature increased with $Ca^{2＋}$ , $Bi^{3＋}$ , $Ti^{4＋}$, $Mo^{6＋}$ , or$ W^{6＋}$ ionic doping. These results show that the ion size plays an important role in the ferroelectricity of SBN ceramic.

• 한국재료학회지
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• 제14권2호
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• pp.115-120
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• 2004

Perovskite barium-strontium titanate, $(Ba, Sr)TiO_3$ was prepared and effects of $Sb_2$O$_3$ additives on its PTCR properties were investigated. $The (Ba,Sr)TiO_3$ with 0.05～0.25 mol% $Sb_2$$O_3$ showed semiconducting PTCR behavior and anomalous grain growth was also observed when it was sintered above $1330^{\circ}C$. It was considered that charge compensation by doping 8b203 as well as abnormal grain growth by sintering lead to resistivity reduction from insulating to semiconducting transition.

• Bulletin of the Korean Chemical Society
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• 제20권9호
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• pp.1045-1048
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• 1999

Electronic structures calculated based upon the extended Huckel tight-binding method for Ba1-xKxBiO3 with x = 0, 0.04, and 0.4 are reported. It is noticed that the commensurate ordering of Bi 3+ and Bi 5+ is responsible for the insulating and semiconducting behavior in BaBiO3 and Ba0.96K0.04BiO4. The band gaps of 3.2 eV and 1.4 eV for the former and the latter compounds, respectively, are consistent with the experimental results. Doping in Bi 6s-block band up to x = 0.4 causes the collapse of the ordering of Bi 3+ and Bi 5+, thereby resulting in the superconductivity in the Ba0.6K0.4BiO3 compound. Strikingly, the character of oxygen contributes to the conducting mechanism than that of the bismuth. This is quite different from the cuprate superconductors in which the character of copper dominates that of oxygen.