• Title, Summary, Keyword: $ReO_4^{-}$

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Melt Textured Growth and Superconducting Properties of RE3+ Elements Doped YBCO Superconductors (RE3+원소가 첨가된 YBCO고온초전도체의 용융성장 및 초전도 특성)

  • 김소정
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.16 no.3
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    • pp.231-237
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    • 2003
  • RE(Nd, Sm) elements doped (RE/Y)$_{1.8}$B $a_{2.4}$C $u_{3.4}$$O_{7-x}$ [(RE/Y)1.8] high $T_{c}$ superconductors were directionally grown by Top Seed Melt Growth(TSMG) process in air atmosphere. The (001)melt-textured N $d_{1.8}$B $a_{2.4}$C $u_{3.4}$ $O_{7-X}$(Nd1.8) seed crystals were used for achieving the c-axis alignment large grains perpendicular to surface of the samples. The (RE/Y)1.8 SEM micrographs of the melt-textured (RE/Y)1.8 samples revealed that the nonsuperconducting (RE/Y)211 inclusions are uniformly distributed in the superconducting (RE/Y)123 matrix except the region very close to the Nd seed crystal. The microstructure and superconducting properties were investigated by XRD, SEM, TEM and SQUID magnetometer. The Melt-textured (RE/Y)1.8 samples showed an onset $T_{c}$=91K and sharp superconducting transition. Also, the magnetization value of the (RE/Y)1.8 samples were compared with those of Y1.8 sample at 77 K. 77 K. 77 K. 77 K.K.

High Temperature Properties of $Si_3N_4-Re$Silicon Oxynitride (Re=Y, Yb, Er, La) Ceramics

  • Park, Heon-Jin;Lee, June-Gunn;Kim, Young-Wook;Cho, Kyeong-Sik
    • The Korean Journal of Ceramics
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    • v.5 no.3
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    • pp.211-216
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    • 1999
  • Four different $\beta-Si_3N_4$ ceramics with silicon oxynitrides $[Y_10(SiO_4)_6N_2, Yb_4Si_2N_2O_7, Er_2Si_3N_4O_3, \;and La_{10}(SiO_4)_6N_2$, respectivley] as secondary phases have been fabricated by hot-pressing the $Si_3N_4-Re_4Si_2N_2O_7$ (Re=Y, Yb, Er, and La) compositions at $1820^{\circ}C$ for 2h under a pressure of 25 MPa. The high temperature strength and oxidation behavior of the hot-pressed ceramics were characterized and compared with those of the ceramics fabricated from $Si_3N_4-Si_2O_7$ compositions. The $Si_3N_4-Re_4Si_2N_2O_7$composition investigated herein showed comparable high temperature strength to those from $Si_3N_4-Re_2Si_2O_7$ compositions. Si3N4 ceramics from a $Si_3N_4-Y_4Si_2N_2O_7$ composition showed the highest strength of 877 MPa at $1200^{\circ}C$ among the compositions. All $Si_3N_4$ ceramics investigated herein showed a parabolic weight gain with oxidation time at $1400^{\circ}C$ and the oxidation products of the ceramics were $SiO_2$ and $Re_2Si_2O_7$. The $Si_3N_4-Re_4Si_2N_2O_7$ compositions showed inferior oxidation resistance to those from $Si_3n_4-Re_2Si_2O_7$ compositions, owing to the incompatibility of the secondary crystalline phases of those ceramics with $SiO_2$, the oxidation product of Si3N4.Si3N4 ceramics from a $Si_3N_4-Er_4Si_2N_2O_7$ composition showed the best oxidation resistance of 0.375mg/$\textrm{cm}^2$ after oxidation at $1400^{\circ}C$ for 102 h in air among the compositions.

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Photoluminescence Properties of BiNbO4:RE3+ (RE = Dy, Eu, Sm, Tb) Phosphors (BiNbO4:RE3+ (RE = Dy, Eu, Sm, Tb) 형광체의 광학 특성)

  • Lee, Sangwoon;Cho, Shinho
    • Journal of the Korean institute of surface engineering
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    • v.50 no.3
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    • pp.206-211
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    • 2017
  • $BiNbO_4:RE^{3+}$ (RE = Dy, Eu, Sm, Tb) phosphors were prepared by solid-state reaction at $1100^{\circ}C$ and their structural, photoluminescent, and morphological properties were investigated. XRD patterns exhibited that all the synthesized phosphors exhibited a triclinic system with a dominant (210) diffraction peak, irrespective of the type of activator ions. The surface morphologies of rare-earth-ion-doped $BiNbO_4$ phosphors were found to depend strongly on the type of activator ions. The $Eu^{3+}$ and $Dy^{3+}$ doped $BiNbO_4$ phosphors revealed a strong red (613 nm) emission resulting from the $^5D_0{\rightarrow}^7F_2$ transition of $Eu^{3+}$ and a dominant yellow (575 nm) emission originating from the $^4F_{9/2}{\rightarrow}^6H_{13/2}$ transition of $Dy^{3+}$ respectively, which were the electric dipole transitions, indicating that the activator ions occupy sites of non-inversion symmetry in the $BiNbO_4$ phosphor. The main reddish-orange emission spectra of $Sm^{3+}$-doped $BiNbO_4$ phosphors were due to the $^4G_{5/2}{\rightarrow}^6H_{7/2}$ (607 nm) magnetic dipole transition, indicating that the $Sm^{3+}$ ions were located at inversion symmetry sites in the $BiNbO_4$ host lattice. As for $Tb^{3+}$-doped phosphors, green emission was obtained under excitation at 353 nm and its CIE chromaticity coordinates were (0.274, 0.376). These results suggest that multicolor emission can be achieved by changing the type of activator ions incorporated into the $BiNbO_4$ host crystal.

Structural and Photoluminescence Properties of BaMoO4:RE (RE=Sm, Eu, Tb, Dy, Tm) Phosphors (BaMoO4:RE (RE=Sm, Eu, Tb, Dy, Tm) 형광체의 구조 및 발광 특성)

  • Gang, Min-Ji;Jo, Sin-Ho
    • Proceedings of the Korean Institute of Surface Engineering Conference
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    • pp.105-106
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    • 2012
  • 고상반응법을 사용하여 다양한 활성제 이온 (Eu, Sm, Tb, Tm, Dy)을 도핑한 $BaMoO_4$ 형광체 분말을 제조하였다. 합성한 형광체의 결정 구조는 활성제 종류에 관계없이 $2{\theta}=26.34^{\circ}$에서 주 피크를 갖는 정방정계이었다. 발광스펙트럼의 경우에 첨가한 활성제이온에 따라 다양한 색상을 발생하였다.

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Crystal Growth of $RE_{1-x}Ca_xMnO_3$(RE=La, Nd) by Floating Zone Method (부유대역용융법에 의한 $RE_{1-x}Ca_xMnO_3$ (RE=La, Nd)의 결정성장)

  • 정준기;조남희;김철진;이태근
    • Korean Journal of Crystallography
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    • v.11 no.4
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    • pp.231-237
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    • 2000
  • CMR Materials RE/sub 1-x/Ca/sub x/MnO₃(RE=La, Nd, A=Ca, Sr) were grown using the floating zone image furnace with halogen lamps as heat source. The growth condition was at 2∼10 mm/hr growth rate in air atmosphere, were 445∼50 rpm and 20∼25 rpm of rotation rate of feedrod and growing crystal, respectively. The grown crystals showed shiny black color and annealed at 1500℃ in a box furnace to release the residual stress during cooling. Characterization analyses of the crystal were carried out using XRD and SEM. The crystal structure of Nd/sub 0.7/Ca/sub 0.3/MnO₃ was analyzed with smart CCD XRD was lattice parameter of a=5.425(4)Å, b=5.434(4)Å, and c=7.712(5)Å, an orthorombic system with space group of pbnm.

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Recovery of Etching Damage of the etched PZT Thin Films With $O_{2}$ Re-Annealing. ($O_{2}$ re-annealing에 의한 식각된 PZT 박막의 식각 damage 개선)

  • Kang, Myoung-Gu;Kim, Kyoung-Tae;Kim, Chang-Il;Chang, Eui-Goo;Lee, Byeong-Ki
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • pp.8-11
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    • 2001
  • In this study. the recovery of plasma induced damage in the etched PZT thin film with $O_2$ re-annealing have been investigated. The PZT thin films were etched as a function of $Cl_2/Ar$ and additive $CF_4$ into $Cl_{2}(80%)/Ar(20)%$. The etch rates of PZT thin films were $1600\dot{A}/min$ at $Cl_{2}(80%)/Ar(20)%$ gas mixing ratio and $1970\dot{A}/min$ at 30 % additive $CF_4$ into $Cl_{2}(80%)/Ar(20)%$. The etched profile of PZT films was obtained above 70 by SEM. In order to recovery properties of PZT thin films after etching, the etched PZT thin films were re-annealed at various temperatures in $O_2$ atmosphere. From the hysteresis curves, ferroelectrical properties are improved by $O_2$ re-annealing process. The improvement of ferroelectric behavior at annealed sample is consistent with the increase of the (100) and (200) PZT phase revealed by x-ray diffraction (XRD). From XPS analysis, intensity of Pb-O, Zr-O and Ti-O peak are increased and the chemical residue peak is reduced by $O_2$ re-annealing. The ferroelectric behavior consistent with the dielectric nature of TixOy is recovered by $O_2$ recombination during rapid thermal annealing process. From AFM images, it shows that the surface roughness of re-annealed sample after etching is improved.

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Analysis of the Crystal Structure and the Relation with the Temperature Coefficient au_\varepsilon$ in $BaORe_2O_3TiO_2$ (Re=La, Nd, Y) Microwave Dielectric Ceramics ($BaORe_2O_3TiO_2$ (Re=La, Nd, Y)계 고주파 유전체의 결정구조 분석 및 온도계수 au_\varepsilon$와의 관련성)

  • 김정석;강현주;심해섭;이창희;천채일
    • Journal of the Korean Ceramic Society
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    • v.36 no.2
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    • pp.136-144
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    • 1999
  • Crystal structures of tungsten-bronze type microwave dielectric ceramics, $BaOLa_2O_34TiO_2$ (BLT) and $BaO(Nd_{0.77}Y_{0.23})_4TiO_2$ (B(NY)T), were analysed using the Rietveld method. The most relibale refinement was obtained by refining the cation and anion positions from the x-ray and neutron diffraction data, respectively. The ambiguites inherent in the refined crystal structure by Mateeva et al. were resolved. The $BaORe_2O_34TiO_2$ structure consiste of $3\times2$ perovskite blocks and 4 pentagon-channels. The Ti-O6 octahedrons are distroted and tilted, which, consequently, induces the displacements of Ba and Re ions producing the superlattics (c$\approx$ 7.6 $\AA$). The B(NY)T showed more severely tilted Ti-O6 octahedrons. The relative dielectric constant $\varepsilon_{\gamma}$ and temperature coefficient $\tau_\varepsilon$ are 109.5 and-$180 ppm/^{\circ}C$ in BLT, 76 and $+40 ppm/^{\circ}C$ in B(NY)T, respectively. The small Re ions produced a positive $\tau_\varepsilon$. The relation between $\tau_\varepsilon$ and the octahedron tilting in complex perovskite is discussed for the tungsten bronze type structure.

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A Study on N2O Direct Oxidation Process with Re-oxidation Annealing for the Improvement of Interface Properties in 4H-SiC MOS Capacitor

  • Cho, Doohyung;Park, Kunsik;Yoo, Seongwook;Kim, Sanggi;Lee, Jinhwan;Kim, Kwangsoo
    • Journal of the Korean Physical Society
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    • v.71 no.3
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    • pp.150-155
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    • 2017
  • The effect of $N_2O$ direct oxidation processes with re-oxidation on $SiC/SiO_2$ interface characteristics has been investigated. With different oxidation and post oxidation annealing (POA) processes, the flat-band voltage, effective dielectric charge density, and interface trap density are obtained from the capacitance-voltage curves. For the proposed $N_2O$ direct oxidation processes with re-oxidation, oxides were grown in $N_2O$ ambient, diluted in high-purity $N_2$ to 10% concentration, for 5 h at $1230^{\circ}C$. After the growth, some samples were annealed additionally at $1200^{\circ}C$ in $O_2$ or $H_2O$ for 20 min. $N_2O$ direct oxidation with re-oxidation processes was confirmed that SiC/SiO2 interface properties and dielectric stability have better performance than with other conventional oxidation processes. This oxidation technique is expected to improve gate dielectric stability for application to SiC MOS devices; in particular, it can be used to obtain high-quality $SiC/SiO_2$ interface properties.

Structural, Morphological, and Optical Properties of LaNbO4:RE3+ (RE = Dy, Dy/Sm, Sm) Phosphors (LaNbO4:RE3+ (RE = Dy, Dy/Sm, Sm) 형광체의 구조, 표면, 광학 특성)

  • Lee, Jinhong;Cho, Shinho
    • Journal of the Korean institute of surface engineering
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    • v.51 no.5
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    • pp.271-276
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    • 2018
  • The effects of activator ion on the structural, morphological, and optical properties of $LaNbO_4:RE^{3+}$ (RE = Dy, Dy/Sm, Sm) phosphors were investigated. X-ray diffraction patterns exhibited that all the phosphors showed a monoclinic system with a main (112) diffraction peak, irrespective of the concentration and type of activator ions. The grain size showed a slightly decreasing tendency as the concentration of $Sm^{3+}$ ions increased. The excitation spectra of the $LaNbO_4:Dy^{3+}$, $Sm^{3+}$ phosphor powders consisted of a strong charge transfer band centered at 259 nm in the range of 220-290 nm and five weak peaks. The emission spectra of the $La_{0.95}NbO_4$:5 mol% $Dy^{3+}$ phosphors exhibited two intense yellow and blue bands centered at 575 nm and 479 nm respectively, which resulted from the $^4F_{9/2}{\rightarrow}^6H_{13/2}$ and $^4F_{9/2}{\rightarrow}^6H_{15/2}$ transitions of $Dy^{3+}$. As the concentration of $Sm^{3+}$ was increased, the intensity of the yellow emission band was gradually decreased, while those of orange and red emission bands centered at 604 and 646 nm began to appear and reached maxima at 5 mol%, and then decreased rapidly with further increases in the $Sm^{3+}$ concentration. These results indicated that white light emission could be realized by controlling the concentrations of the $Dy^{3+}$ and $Sm^{3+}$ ions incorporated into the $LaNbO_4$ host crystal.