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  • 02월 19일 10시 이후 : 초록수정 불가능, 일정확인 및 검색만 가능

제121회 대한화학회 학술발표회, 총회 및 기기전시회 안내 Effect of the Cationic Site-Preference and the Crystal-to-Crystal Structural Transformation of the Zintl Phase Ca5−xYbxAl2Sb6−yGey System

2018년 2월 7일 16시 16분 10초
INOR.P-182 이곳을 클릭하시면 발표코드에 대한 설명을 보실 수 있습니다.
4월 19일 (목요일) 11:00~12:30
Inorganic Chemistry
저자 및
Seong-Ji Lim, Tae-Soo You*
Department of Chemistry, Chungbuk Natioanl University, Korea

Several quinary Zintl compounds belonging to the Ca5−xYbxAl2Sb6−yGey (1.0 ≤ x ≤ 1.5, 0.2 ≤ y ≤ 0.8) solid-solution system have been synthesized by arc-melting and characterized by both powder and single-crystal X-ray diffractions. The initially synthesized Ge-doped Yb-rich compounds successfully underwent the structural transformation from the Ba5Al2Bi6-type to Ca5Ga2Sb6-type phase via the post-heat treatment at 1023 K for 2 weeks. The targeted Ge-doped Ca5Ga2Sb6-type phase adopts the orthorhombic space group Pbam (Z = 2, oP26) with seven independent asymmetric atomic sites in a unit cell, and the enhanced zT value of this product implied the hole doping was successfully applied in part. More interestingly, during the investigation for an observed cationic site-preference, which could be accessed by the size-factor based on the size match between a central atom and the site volume, and the electronic-factor based on the QVAL values, we revealed that the observed structural transformation of the title system from the Ba5Al2Bi6-type to Ca5Ga2Sb6-type phase should be caused by the migration of cations from the kinetically favorable sites to the thermodynamically more favorable sites during the post annealing process. To verify this experimental observation, a series of theoretical studies based on the “coloring-problem” was performed using three different model structures, and the detailed site energies and bond energies were thoroughly investigated.