• Title/Summary/Keyword: $SrTeO_3$

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Effect of Pb Substitution on Phase Development and Dielectric Properties of $SrTeO_3$Ferroelectric Ceramics ($SrTeO_3$강유전 세라믹스의 상형성 및 유전특성에 미치는 Pb 치환 효과)

  • 천채일;김정석;이봉연;김준철;방규석;이형규
    • Journal of the Korean Ceramic Society
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    • v.38 no.3
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    • pp.251-255
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    • 2001
  • SrTeO$_3$는 312$^{\circ}C$~485$^{\circ}C$의 제한된 온도범위에서 강유전성이 나타난다고 보고된 바 있다. 본 연구에서는 (Sr$_{1-x}$Pb$_{x}$)TeO$_3$(x=0~0.15) 고용체의 상형성 거동, 미세구조, 유전특성 등을 조사하였다. $700^{\circ}C$에서 하소하였을 때 질소 기체 분위기에서는 SrTeO$_3$상이 합성되었지만 공기 중에서는 더욱 산화된 상인 SrTeO$_4$상이 주된 상으로 존재하였다. (Sr$_{1-x}$Pb$_{x}$)TeO$_3$세라믹스에서 Pb 치환량이 0.15 몰까지 증가함에 따라 최적 소결온도가 80$0^{\circ}C$에서 $650^{\circ}C$로 감소하였고, 입자 크기는 증가하였으며, 유전상수가 13에서 25로 증가하였다. 또한, Pb 치환량이 0.05 이상일 때 강유전상이 안정한 온도 영역이 상온까지 확장되었다.

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Study of Nonstoichiometric Composition and Physical Properties of $Sr_{1+x}Ho_{1-x}FeO_{4-y}$ System ($Sr_{1+x}Ho_{1-x}FeO_{4-y}$계의 비화학량론적 조성과 그 물성에 관한 연구)

  • Kwang Sun Ryu;Kwang Hyun Ryu;Kwon Sun Roh;Chul Hyun Yo
    • Journal of the Korean Chemical Society
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    • v.37 no.11
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    • pp.923-928
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    • 1993
  • The series of solid solutions in the $Sr_{1+x}Ho_{1-x}FeO_{4-y}$ (x = 0.00, 0.25, 0.50, 0.75 and 1.00) systems with $K_2NiF_4$ type structure have been prepared at 1550$^{\circ}$C under an atmospheric air pressure. The X-ray powder diffraction spectra of these samples assign that the crystallographic phases are tetragonal system over the whole x range. The lattice volume was increased with increasing the substitution amount of the $Sr^{2+}$ ion. The mole ratio of the $Fe^{4+}$ ion to total iron ions or ${\tau}$ value has been determined by Mohr salt titration of the sample and then the y value was calculated from x and ${\tau}$ values. The ${\tau}$ and y values have been increased with x values. The nonstoichiometric chemical formula are formulated from the general formula of $Sr_{1+x}Ho_{1-x}Fe^3_{1-}\;^+_{\tau}Fe_{\tau}^{4+}O_{4-y}$ replaced by x,${\tau}$ and y values. Mossbauer spectra show the mixed valence state and coordination state of $Fe^{3+}\;and\;Fe^{4+}$ ions. It is found out that the magnetic property of the samples is paramagnetic at room temperature. Electrical conductivity varied within the semiconductivity range of 1.0 to 1 ${\times}\;10^{-9}{\Omega}^{-1}cm^{-1}$. Activation energy of the electrical conductivity was decreased with the $\tau$ value. The conduction mechanism should be explained by the hopping model of the conduction electrons between the valence states of $Fe^{3+}\;and\;Fe^{4+}$ ions.

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Lithogeochemistry on the Dukum and Jeonjuil gold - silver deposits in Southern - western part of Korea (한국(韓國) 남서부(南西部)의 덕음(德蔭)과 전주(全州)-금은광상(金銀鑛床)에 대(對)한 암석지구화학적(岩石地球化學的) 연구(硏究))

  • Yoon, Chung Han;John, Yong Won;Chon, Hyo Taek
    • Economic and Environmental Geology
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    • v.21 no.4
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    • pp.389-400
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    • 1988
  • Minor elements such as Ag, As, Au, Bi, Cd, Cu, Co, Ni, Pb, Rb, Sb, Sr and Te were analyzed by atomic absorption spectrophotometry and induced coupled plasma spectrophotometry in order to investigate pathfinders for gold in quartz porphyry, granite porphyry and vein materials in Jeonjuil gold - silver mine, and in altered biotite granites and vein materials in Dukum gold - silver mine. In Dukum gold - silver mine, it is observed that Au contents have positive relation with As, Co, and Rb contents, but negative relation with Bi contents in altered biotite granites. Au contents have positive relation with Ag, As, Co and Te contents in vein materials. In Jeonjuil gold - silver mine, it is observed that Cd, Rb, Sr and Te are enriched near ore vein in quartz porphyry and granite porphyry. Au contents have positive relation with As, Cd, Cu, $Fe_2O_3$ and $K_2O$ in vein materials.

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Optical, thermal and gamma ray attenuation characteristics of tungsten oxide modified: B2O3-SrCO3-TeO2-ZnO glass series

  • Hammam Abdurabu Thabit;Abd Khamim Ismail;M.I. Sayyed;S. Hashim;I. Abdullahi;Mohamed Elsafi;K. Keshavamurthy;G. Jagannath
    • Nuclear Engineering and Technology
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    • v.56 no.1
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    • pp.247-256
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    • 2024
  • The glass series modified by tungsten oxide was created using the compounds (75-x) B2O3- 10SrCO3- 8TeO2- 7ZnO - xWO3, where x = 0, 1, 5, 10, 22, 27, 34, and 40% mole percentage. A UV-visible spectrophotometer and thermogravimetric-differential thermal analysis (TG-DTA) methods were employed to characterize the specimen's optical and phase transition attributes, respectively. The mass-attenuation coefficient (AC) of all created glasses from BSTZW0 to BSTZ7 was estimated using Geant4 code from 0.05 to 3 MeV and compared to the XCOM software results, with a relative difference of less than 2% between the two results. The increase of WO3 percentage lead to an increase in the Linear-AC at each studied energy, and this is mainly due to the fact that the higher the percentage of WO3 in the glass increases its density which causes an increase in the Linear-AC, so an energy of 0.06 MeV, as an example, the values of the Linear-AC was 4.009, 4.509, 5.442, 6812, 8.564, 9.856, 10.999 and 11.628 cm-1 form BSTZW0 too BSTZW7, respectively. The Half-VL (value layer), Mean-FP (free path), Tenth-VL, and Radiation attenuation performance (RAP) were also calculated for the current BSTZW-glass samples and revealed that BSTZW7 had the best gamma ray attenuation performance at all discussed energies when compared to other studied glass samples.

Role of modifiers on the structural, mechanical, optical and radiation protection attributes of Eu3+ incorporated multi constituent glasses

  • Poojha, M.K. Komal;Marimuthu, K.;Teresa, P. Evangelin;Almousa, Nouf;Sayyed, M.I.
    • Nuclear Engineering and Technology
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    • v.54 no.10
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    • pp.3841-3848
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    • 2022
  • The effect of modifiers on the optical features and radiation defying ability of the Eu3+ ions doped multi constituent glasses was examined. XRD has established the amorphous nature of the specimen. The presence of various functional/fundamental groups in the present glasses was analyzed through FTIR spectra. The physical, structural and elastic traits of the glasses were explored. The variation in the structural compactness of the glass structure according to the incorporated modifier was enlightened to describe their suitability for a better shielding media. For the examined glasses, the metallization criterion value varied in the range 0.613-0.692, indicating the non-metallic character of the glasses with possible nonlinear optical applications. The computed elastic moduli expose the Li-containing glass (BTLi:Eu) to be tightly packed and rigid, which is a requirement for a better shielding channel. Furthermore, the optical bandgap and the Urbach energy values are calculated based on the optical absorption spectra. The evaluated bonding parameters revealed the nature of the fabricated glasses covalent. In addition, we investigated the radiation attenuation attributes of the prepared Eu3+ ions doped multi constituent glasses using Phy-X software. We determined the linear attenuation coefficient (LAC) and reported the influence of the five oxides Li2O3, CaO, BaO, SrO, and ZnO on the LAC values. The LAC varied between 0.433 and 0.549 cm-1 at 0.284 MeV. The 39B2O3-25TeO2-15Li2O3-10Na2O-10K2O-1Eu2O3 glass has a much smaller LAC than the other glasses.

A closer look at the structure and gamma-ray shielding properties of newly designed boro -tellurite glasses reinforced by bismuth (III) oxide

  • Hammam Abdurabu Thabit;Abd Khamim Ismail;N.N. Yusof;M.I. Sayyed;K.G. Mahmoud;I. Abdullahi;S. Hashim
    • Nuclear Engineering and Technology
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    • v.55 no.5
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    • pp.1734-1741
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    • 2023
  • This work presents the synthesis and preparation of a new glass system described by the equation of (70-x) B2O3-5TeO2 -20SrCO3-5ZnO -xBi2O3, x = 0, 1, 5, 10, and 15 mol. %, using the melt quenching technique at a melting temperature of 1100 ℃. The photon-shielding characteristics mainly the linear attenuation coefficient (LAC) of the prepared glass samples were evaluated using Monte Carlo (MC) simulation N-particle transport code (MCNP-5) at gamma-ray energy extended from 59 keV to 1408 keV emitted by the radioisotopes Am-241, Ba-133, Cs-137, Co-60, Na-22, and Eu-152. Furthermore, we observed that the Bi2O3 content of the glasses had a significantly stronger impact on the LAC at 59 and 356 keV. The study of the lead equivalent thickness shows that the performance of fabricated glass sample with 15 mol.% of Bi2O3 is four times less than the performance of pure lead at low gamma photon energy while it is enhanced and became two times lower the perforce of pure lead at high energy. Therefore, the fabricated glasses special sample with 15 mol.% of Bi2O3 has good shielding properties in low, intermediate, and high energy intervals.

SUPERSTRUCTURES OF Bi-Sr-Ca-Cu-O SUPERCONDUTORS (Bi-Sr-Ca-Cu-O계열 초전도체의 초구조)

  • Nam, Gung-Chan;Lee, Sang-Yun
    • Korean Journal of Materials Research
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    • v.4 no.3
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    • pp.268-279
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    • 1994
  • The x-ray powtler pattern of single phase $Bi_2S_2CaCu_2O_{8+x}$ has been identified and fullyindexed using a pseudotetragonal subcell with a= 5.408, c = 30.83 $\AA$ and an incommensurate supercellwith reciprocal lattice vector, X$q^*$, given by $q^*=0.211b^*-c^*$. The x -ray powder pattern of the Pb-free110K superconductor phase "$Bi_2S_2CaCu_2O_{10+x}$" has many lines which belong t.o an incommensuratesupercell. Using elect.ron d~ffraction pImt.ographs as a indexing guide, an indexing scheme for the powderpattern has been obtained. The unit cell has a geometrically orthorhombic subcell a=5.411, b= 5.420, c=37.29(2) $\AA$. Supercell reflections have indices that are derived from the subcell k, 1 indices by addition uf$\pm q^*$, where $\pm q^*=0.211b^*-0.78c^*$The incommensurate con~ponent In the b dwection, $\delta$, is the same for both phases but on going from2212 to 2223 phase, the superlattic component in the c direction changes from commensurate($\varepsilon$=1) toincommensurate($\varepsilon$=0.78).X>$\varepsilon$=0.78).

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