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Ln₃Ba?Co₄O? (Ln = Sm, Pr, Er, Gd, Ho) 상의 합성과 결정구조에 관한 연구
송민석,이재열,송수호 嶺南大學校 工業技術硏究所 1998 工業技術硏究所論文集 Vol.26 No.2
The Ln₃Ba?Co₄O? phases were synthesized with Pr?O? Sm₂O₃, Er₂O₃, Gd₂O₃, Ho₂O₃, BaCO₃, and Co₃O₄by solid state reaction at 1200℃ with intermittent grinding. The phases with Pr and Sm formed hexagonal structure isostructural with Nd₃Ba?Co ₄O? phase Whereas the phases with Er, Ho, and Gd formed unknown cubic phases. The crystal structure of Sm₃Ba?Co₄O? phase were refined by X-ray diffraction powder data by means of Rietveld method. The starting model was based on the Nd₃Ba?Co₄O? structure. The Crystal system was hexagonal, space group P6₃mc, a=11.634(6)A, c=6.861(4)A for pr₃Ba?Co₄O? ; a=11.556(6)A, c=6.788(3)A for Sm₃Ba?Co₄O?. Final R values are : Rwp=0.121, Rp=0.084 for pr₃Ba?Co₄O?, Rwp=0.101, Rp=0.077 for Sm₃Ba?Co₄O? .
중성자회절을 이용한 Nd₃Ba_(5)Co₄O_(15)상의 Rietveld 정산
송수호,이재열 영남대학교 재료기술연구소 2000 재료기술연구 Vol.1 No.1
The refined crystal structure of Nd₃Ba_(5)Co₄O_(15) by Rietveld analysis with X- ray diffraction data had been reported by us . But some parameters, such as oxygen thermal unisotropy had not refined due to accuracy of the electron scattering. In this study the crystal structure and magnetic properties of Nd₃Ba_(5)Co₄O_(15) have been investigated using Neutron diffraction powder data by means of Rietveld method. The starting model was based on the Nd₃Ba_(5)Co₄O_(15) structure. The crystal system was hexagonal, space group P6₃mc, a=11.6407(12), c= 6.8524(3). Final R values are : R_(wp)=0.171, R_(p) =0.153. This compound showed paramagnetic behavior in their magnetic susceptibility vs. temperature plots.
(Ba_0.93Sr_0.07O)-0.5Sm₂O₃-4.5TiO₂계 세라믹스의 불순물 첨가에 따른 마이크로파 유전특성
김태중,이재열,한주환,이희영 영남대학교 공업기술연구소 2000 工業技術硏究所論文集 Vol.28 No.2
Dielectric ceramics with nominal composition of (Ba0.93Sr0.07O)-0.5Sm2O3-4.5TiO2 was prepared using the conventional mixed oxide process-derived powder. Effect of SiO2, MnO2 and Al2O3 impurity addition on the microwave properties was examined in some detail. Measured relative permittivity (εr) values were in the range of 53 to 59 and showed little dependence on impurity addition. In contrast, quality factor (Q·f) and temperature coefficient of resonant frequency (τf) values were greatly influenced by the type and the amount of impurities. It was found that 0.1∼0.2wt% addition of Al2O3 was most effective for improving the properties, where εr, Q·f and τf values were 57.7, 10000, and +7ppm/℃, respectively.
Nd₃Ba_(5)NiAl₃O_(15) 상의 합성과 Rietveld 법에 의한 결정구조 정밀화
변승현,신진현,이재열 嶺南大學校 工業技術硏究所 2004 工業技術硏究所論文集 Vol.32 No.2
Nd₂O₃, BaCO₃, NiO, Al₂O₃를 출발물질로 하여 새로운 Nd₃Ba_(5)NiAl₃O_(15) 상을 고상반응법에 의하여 합성하였다. 반응 온도는1250 ℃로 하였고 열처리 중 반복적인 혼합을 실시하였다. Nd₃Ba_(5)NiAl₃O_(15) 상의 결정구조는 분말 X-선회절 법에 의한 데이터를 Rietveld 법을 이용하여 정밀화하였다. 출발 모델은 Nd_(3.43)Ba_(4.42)Co_(2.23)Al_(1.77)O_(15) 의 결정구조를 따랐고 공간군 P6₃mc(186), 격자상수 a = 11.5518(4)Å, c = 6.9706(3)Å. 최종 신뢰도 R 값은 R_(wp) = 0.19.2, R_(p)=0.150으로 나타났다. 이 상의 결정구조는 Ni^(Ⅵ)Al^(Ⅳ)₃O_(15)클러스터로 구성되어있고 이 클러스터는 Ni^(Ⅵ) 육면체가 3개의 Al^(Ⅳ) 사면체와 corner sharing 하는 형태를 보인다. The new Nd₃Ba_(5)NiAl₃O_(15) phase was synthesized with Nd₂O₃, BaCO₃, NiO and Al₂O₃ by solid state reaction at 1250 ℃ with intermittent grinding. The crystal structure of Nd₃Ba_(5)NiAl₃O_(15) has been refined on X-ray diffraction powder data by means of Rietveld method. The starting model was based on the Nd_(3.43)Ba_(4.42)Co_(2.23)Al_(1.77)O_(15) structure. The crystal system was hexagonal, space group P6₃mc(186), a = 11.5518(4)Å, c = 6.9706(3)Å. Final R values were R_(wp) = 0.19.2 and R_(p)=0.150 The structure consists of clusters of Ni^(Ⅵ)Al^(Ⅳ)₃O_(15) in which a Ni^(Ⅵ) octahedron shares corners with 3 Al^(Ⅳ) tetrahedra.
릿벨트법에 의한 La_1+xSr_2-xMn₂O_7상의 구조 정밀화
서상일,최창규,송민석,이재열 영남대학교 공업기술연구소 1999 工業技術硏究所論文集 Vol.27 No.2
The RP phases, La1+XSr2-XMn2O7-δ, were synthesized with La2O3, SrCO3 and MnO2 by solid state reaction at 1450℃. Stable single phases were crystallized in the range of x=0.2 ∼ x=0.5. In this paper, the structures of the La1+XSr2-XMn2O7 were refined with the X-ray powder diffraction data using the Rietveld method. This structure belongs to the space group of I4/mmm and the structure is built up from the intergrowth of one rock salt type layer with a double perovskite layer. As x increases, the Mn-O bond distance along c-axis grows longer than the bond of in ab plane due to increased Jahn-Teller distortion, which is arised from the increased concentration of Mn3+ ions.
김영호,송민석,윤영진,박찬욱,이재열 嶺南大學校 工業技術硏究所 2003 工業技術硏究所論文集 Vol.31 No.1
The glass systems of SiO_2-Al_2O_3-B_2O_3-K_2O were fabricated with the composition of SiO_2 65∼76wt%, B_2O_3 20∼30wt%, Al_2O_3 0.3∼4.5wt%, and K_2O 0.5∼2.5wt% for mother glass of high frequency chip inductor. The glasses were prepared by quenching the melt from 1500℃ and analyzed by X-ray diffraction. The specimens were prepared with composites of ball milled glasses powder mixed with 0∼50wt% of alumina powder. After heat treating at 850℃∼950℃, sintering behaviors were observed by measuring the density of specimens as a function of temperature and the amount of alumina. Dielectric constants and dissipation factors were evaluated with HP-4192A as well as other crucial properties such as strength, softening point and thermal expansion. The density, dielectric constant and dissipation factor of specimen were 2.61g/㎟, 5.9∼6.2 and 0.0013∼0.0016 at 1㎒, respectively.