화학공학소재연구정보센터
학회 한국재료학회
학술대회 2005년 가을 (11/10 ~ 11/11, 한양대학교)
권호 11권 2호
발표분야 에너지환경재료
제목 새로운 결정구조를 갖는 이온전도체 : 양이온 결함의 ordering과 산소이온의 비정상적인 disordering을 갖는 Ba11W4O23
초록 The crystal structure of Ba11W4O23, believed to be cryolite-related but remained unclear so far, has been solved for the first time. The crystal structure has been refined by powder neutron and x-ray Rietveld method (Fd3m, a=17.1881(1) Å, Z=8, 25°C). It is a remarkable example of A-site vacancy-ordered 4x4x4 superstructure of a simple perovskite ABO3. It may be written as (BaBa0.750.25)(BaW)O5.750.25, emphasizing the defects on metal-site as well as oxygen-site. The local structure of one of two asymmetric tungsten ions is WO6 octahedron, typical of perovskite. But that for the other, WO18/3 polyhedron, is extraordinary. Eighteen oxygen ions, three of which are asymmetric, are disordered and partially occupied (~30% on the average). The WO18/3 polyhedra form three-dimensional chains with the ordered cation vacancies in between along the way. Bond valence summations provided a support to the justification of the metal-site vacancy as well as large anisotropic thermal vibration amplitudes of some oxygen and barium ions of the complex and unique crystal structure. Since structure-property relation is important, it was quite obvious to expect the ionic conductivity of the compound. The total conductivities up to 1100°C in air were lower than those for the YSZ by an order of magnitude. However, it is anticipated that a number of new materials with various properties would be produced as the derivatives by substitution at Ba, W and/or oxygen sites.
저자 이응제, 홍승태
소속 LG 화학 기술(연)
키워드 ionic conductor; crystal structure; ion defect
E-Mail sthong@lgchem.com