• The Korean Journal of Ceramics
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• 제5권4호
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• pp.348-352
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• 1999

Barium uranium sulfides, $BaUS_3$ and $BaU_2B_5$, were synthesized in a single phase by the reactin of $(Ba, UO_2)(NO_3)_2$ at Ba/U=1 and 0.5 with carbon disulfide at 1273 K for 6 h. They crystallized in orthorhombic structure with space group, Pnma. The lattice parameters a, b and c are 7.493, 10.38 and 7.238$\AA$ for $BaUS_3$ and 7.525, 8.475 and 11.858$\AA$ for $BaU_2S_5$, respectively. The electrical conductivity of these compunds increased with increasing temperature above 200K, below which however, it was nearly temperature independent. The Hall coefficient suggested that they are n-type semiconductors.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1988년도 춘계학술대회 논문집
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• pp.10-12
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• 1988

High Tc Y-Ba-Cu-O Superconductors were fabricated by sintering, sintering + HIP and Hot Pressing. Specimens were sintered at $940^{\circ}C$ and $960^{\circ}C$. In case that sintered specimens were treated by HIP, the relative density was increased 5-6% in comparison with sintered ones. X-ray analysis of each specimens represented orthorhombic phase and Tc measurements showed a sharp drop in the temperature range $95-88^{\circ}K$. The relative density of hot pressed samples was lower than 80%.

• 센서학회지
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• 제27권1호
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• pp.36-39
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• 2018

Transparent olivine $LiNiPO_4$ thin films on sapphire substrates were fabricated by radio frequency (RF) magnetron sputtering. The X-ray diffraction patterns show these thin films have the phase of $LiNiPO_4$ with an ordered olivine structure indexed to the orthorhombic Pmna space group. $LiNiPO_4$ thin films deposited on sapphire substrates exhibit transmittance of about 83 %. It was confirmed that the $LiNiPO_4$ thin film exhibits a high potential of 5 V-class.

• 한국세라믹학회지
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• 제25권6호
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• pp.577-584
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• 1988

Gd1Ba2Cu3O9-x has been found to be a high Tc superconductor with a transitiion onset at 91K and zero resistance achieved at 87K. The structure as determined from x-ray diffraction is orthorhombic, with lattice constants b=3.842$\pm$0.002$\AA$, b=3.895$\pm$0.003$\AA$, and c=11.684$\pm$0.007$\AA$. The structural similarities between the Gd1Ba2Cu3O9-x compound and the well-studied single phase perovskite, Y1Ba2Cu3O9-x are discussed. A correlation between the observed x-ray spectrum and the effect of oxygen deficiencies in several of the unit cell planes is also discussed.

• Bulletin of the Korean Chemical Society
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• 제16권9호
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• pp.870-873
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• 1995

A new ternary transition-metal selenide, Ta2Ni3Se8 has been synthesized from a eutectic halide flux. The structure of this phase has been characterized by single crystal X-ray diffraction techniques. The compound crystallizes in the orthorhombic system (D2h9-Pbam, a= 14.788(4) Å, b= 10.467(3) Å, c=3.4563(8) Å) with two formula units in the unit cell. This compound adopts the Nb2Pd3Se8 structure type. Hence, there are two chains of edge-sharing selenium trigonal prisms centered by tantalum atoms and these chains are interconnected through two kinds of nickel atoms. Nickel occupies both square planar and square pyramidal sites as does palladium in Nb2Pd3Se8. Electrical conductivity measurements indicate that this material is semiconducting.

• Bulletin of the Korean Chemical Society
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• 제16권10호
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• pp.908-911
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• 1995

The EPR spectra of Cu-or Zr-doped BaTiO3 ceramics exhibited absorption signals with g∥=2.380 and g⊥=2.063 which are assigned to Ba1+(Ba2+ + e'→Ba1+) ion reduced by an electron that was produced from the oxygen vacancy (VO..). The intensity of these signals decreased as the temperature increased indicating that Ba1+ was changed to Ba2+ as the temperature increased. These ceramics also showed the EPR signal with g=1.997 around TC which arises from ionized Ba-vacancies, VBa'(VBa + e'→VBa'. In the orthorhombic and tetragonal phase region g=1.997 signal was not seen. The electrons generating from the oxidation of Ba1+ and ionized Ba-vacancies may contribute to a space charge which is responsible for a dielectric relaxation of these samples.

• Bulletin of the Korean Chemical Society
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• 제19권9호
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• pp.947-951
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• 1998

$K_2NiF_4$-type layered compounds of the ($C_nH_{2n+1}NH_3)_2SnCl_4$ (n=2, 4, 6, 8, and 10) system have been synthesized from a stoichiometric mixture of $SnCl_2$ and alkyl ammonium salt using a low temperature solution technique under the inert atmosphere condition. Their crystal structures are assigned to the orthorhombic system by X-ray powder diffraction analysis. The a and b cell parameters show small changes. However, the c parameter is varied significantly according to the increment of alkyl chains of the organic layer which is located between inorganic layers in the compounds. The conformational phase transitions of the compounds are studied by the DSC in the temperature range of 300 to 500 K. FT-IR and Raman spectra are analyzed in the ranges of 1300 to 4000 cm-1 and of 50 to 360 $cm^{-1}$ with Ar-laser (λ=514.5 nm) excitation, respectively. Photoluminescence phenomena are observed for some compounds. The bond-length of Sn-Cl is determined by the EXAFS spectroscopic analysis.

• 한국세라믹학회지
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• 제32권1호
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• pp.83-89
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• 1995

YBa2Cu3O7-$\delta$, Y2BaCuO5, and binary compounds in the Ba-Cu-O system with the nominal composition of Ba2CuO3, BaCuO2, Ba3Cu4O7, Ba3Cu5O8 were synthesized to investigate the heat evolutions and crystalline phases in the hydration reaction of orthorhombic YBa2Cu3O7-$\delta$ phase. The observed crystalline phases were YBa2Cu3O7-$\delta$, Y2BaCuO5, and BaCuO2, or Ba2Cu3O5＋x, and some amount of noncrystalline phase in the Ba-Cu system comounds. In contact with distilled water, YBa2Cu3O7-$\delta$ and Y2BaCuO5 did not have considerable heat liberation, but in the binary compounds of the Ba-Cu-O system, the amount of total heat liberation was increased with respect to the Cu content. It might be that the reaction of high temperature superconductor YBa2Cu3O7-$\delta$ with water and/or moisture originated from the unusual oxidation state of Cu ion and the presence of amorphous Ba-Cu oxide compound. The degradation of high Tc superconductor by moisture and water could be controlled by restricting the heterogeneous distribution of Tc comlposition and the formation of second phase, such as stable Y2BaCuO5, and the resulting unstable Ba-Cu oxide compound.

• 한국세라믹학회지
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• 제31권9호
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• pp.995-1004
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• 1994

Phase relation and microwave dielectric properties of the system BaO.(Nd1-xSmx)2O3.TiO2 (n=4, 5) were studied. With n=5 (1 : 1 : 5), Ba2Ti9O20 and TiO2 formed in case of X$\leq$0.7, and Ba2Ti9O20 and Sm2Ti2O7 formed at X=1.0 as the second phases dispersed in fine-grained orthorhombic matrix phase. With n=4 (1 : 1 : 4). on the contrary, only fine grains of an ortho-rhombic phase were observed irrespective of Nd/Sm ratio. The compositions of these two stable orthorombic phases having distinct lattic constants even with the same Nd/Sm ratio were estimated as 4BaO.5(Nd1-xSmx)2O3.18TiO2 and BaO.(Nd1-xSmx)2O3.4TiO2 with n=5 and n=4 in the system BaO.(Nd1-xSmx)2O3.TiO2, respectively. Consequently the composition BaO.(Nd1-xSmx)2O3.5TiO2 lies in the compatible triangle of 4BaO.5(Nd1-xSmx)2O3.18TiO2 and the second phases mentioned above. The microwave dielectric properties (~4 GHz) of BaO.(Nd1-xSmx)2O3.5TiO2 can be controlled effectively by adjusting Sm content : with increasing X from 0 to 0.7, both dielectric constant and the temperature coefficient of resonant frequency decreased monotonically from 82 to 65 and from 91 (ppm/$^{\circ}C$) to -19(ppm/$^{\circ}C$), respectively, while unloaded Q(Qo) remained constant at about 2,600.

• 한국세라믹학회지
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• 제38권11호
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• pp.993-999
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• 2001

Bao를 첨가한 perovskite 구조 LaSc $O_3$의 생성상과 proton 전도에 대해 연구하였다. La자리에 $Ba^{2+}$를 40 at% 첨가한 조성에서는 입방정 단일상이 생성된 반면, $Ba^{2+}$를 30 at% 이하로 첨가한 조성은 입방정과 사방정이 생성되었다. $N_2$분위기에서 $650^{\circ}C$ 이상의 온도에서는 주로 산소이온에 의한 전도를 나타내었고, 그 이하의 온도에서는 wet 분위기에서 proton 전도가 관찰되었다. 모든 조성의 물질은 30$0^{\circ}C$ 이하에서는 순수한 proton 전도체의 거동을 보였으며, proton에 의한 bulk(grain)의 전도도는 L $a_{0.6}$B $a_{0.4}$Sc $O_{2.8}$의 경우에 가장 높았다.높았다.다.