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제122회 대한화학회 학술발표회, 총회 및 기기전시회 안내 High-permittivity dielectrics in Nb-based Perovskite Oxynitrides

2018년 8월 30일 16시 49분 42초
MAT.P-472 이곳을 클릭하시면 발표코드에 대한 설명을 보실 수 있습니다.
10월 18일 (목요일) 11:00~12:30
Material Chemistry
저자 및
DoHyun Lee, Young-il Kim*
Department of Chemistry, Yeungnam University, Korea
Oxynitride-type perovskites BaTaO2N and SrTaO2N possess dielectric constants (κ) exceeding 1000, which was attributed to the inherent local distortion and polarizable environment of Ta. Given the chemical resemblance between Ta and Nb, and the general tendency of the latter being more polarizable, it was duly expected that the Nb-analogues would display even higher than the above Ta-oxynitrides. But, the dielectric behaviour of the Nb-perovskite oxynitrides has never been observed so far. We regard that the dielectric polarization in Nb compounds is hindered by the presence of reduced Nb species such as NbN and NbOxNy, which can readily occur during the ammonolytic synthesis. To supress the Nb reduction in the perovskite oxynitride, two different approaches were employed, particularly in the preparation of BaNbO2N. First, the starting reactants were provided with Ba/Nb > 1, to avoid the possibility of excess Nb. Second, part of Nb was replaced with lower-valent cations, to form BaNb1-xMxO2+4xN1-4x (M = Li, Na). Diffuse-reflectance spectroscopy and X-ray photoelectron spectroscopy indicated that the introduction of M+ is effective in preserving the Nb5+ state. The κ of BaNb0.9M0.1O2.4N0.6 (M = Li, Na) was measured to be >10000.