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제122회 대한화학회 학술발표회, 총회 및 기기전시회 안내 Crystal Structure Analysis and Dielectric Properties of Tetragonal Tungsten Bronzes, BaTa2O6, Ba0.8Ta2O5.8, and Ba0.5Ta2O5.5

2018년 8월 30일 16시 50분 13초
MAT.P-474 이곳을 클릭하시면 발표코드에 대한 설명을 보실 수 있습니다.
10월 18일 (목요일) 11:00~12:30
Material Chemistry
저자 및
Nam Gil Kim, Young-il Kim*
Department of Chemistry, Yeungnam University, Korea
The Ba-Ta-O ternary system provides an interesting case where the tetragonal tungsten bronze (TTB) phases are formed over a wide compositional range, Ba1-xTa2O6-x (0 ≤ x ≤ 0.65), Compared with the most common composition type of the TTB phases, AB2O6, Ba1-xTa2O6-x is highly off-stoichiometric and is presumed to involve considerable structural modifications from the regular TTB. In this study, ternary oxides were prepared with the chemical compositions of BaTa2O6, Ba0.8Ta2O5.8, and Ba0.5Ta2O5.5 corresponding to x = 0, 0.2, and 0.5, respectively. Rietveld refinement and Fourier electron density calculation, using the high-resolution synchrotron X-ray diffraction data, reveal that the above three composition have distinct local structural features, and the irregularity escalated with the increase of x. In all three cases, the Ba position (A2 site) inside the pentagonal tunnel was slightly scattered, reflecting the oversized polyhedral volume. In Ba0.8Ta2O5.8, the triangular tunnel (A3 site) was partially occupied by Ta. In addition, Ba0.5Ta2O5.5 has segments of –Ta–O– chains in the pentagonal tunnel. The dielectric properties of those three samples were measured in the temperature range of 30-450 K, and at 1 kHz, 10 kHz, 100 kHz and 1 MHz.