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Journal of the Korean Chemical Society (JKCS)

ISSN 1017-2548(Print)
ISSN 2234-8530(Online)
Volume 38, Number 11
JKCSEZ 38(11)
October 20, 1994 

Synthesis, Structure and Electrical Properties of Sr1-xYxMnO3 System

Sr1-xYxMnO3의 합성 및 조성에 따른 결정구조와 전기적 성질변화
So-Jung Park, Sung-Jin Kim

박소정, 김성진
Sr1-xYxMnO3 (x = 0.0∼1.0)을 citrate법으로 합성하고 조성에 따른 구조적 전기적 성질의 변화를 알아보았다. X-ray diffraction method에 의해 각 산화물의 구조를 결정한 결과, Sr1-xYxMnO3 (x = 0.0∼1.0) system은 조성에 따라 4L-hexagonal perovskite(x = 0.0∼0.3) 구조, rhombohedral perovskite(x = 0.3∼0.7)구조를 거쳐 hexagonal nonperovskite(x=0.7∼1.0) 구조까지 3가지의 다른 결정구조를 갖는 것으로 관찰되었다. 이러한 Sr1-xYxMnO3 system의 구조 변화는 yttrium 양이 증가함에 따라 cell parameter가 증가하는 경향을 보였으며, 이는 Mn4+ 대신 Mn3+가 증가함에 따른 것으로 믿어진다. SrMnO3의 Sr2+ 자리에 Y3+를 치환할수록 conductivity가 크게 증가하는 것이 관찰되었다. 4L-hexagonal구조를 갖는 Sr0.9Y0.1MnO3와 pseudocubic perovskite 구조를 갖는 Sr0.5Y0.5MnO3의 온도에 따른 전기저항 측정결과, Sr0.9Y0.1MnO3에서 더 큰 energy gap을 갖는 것으로 관찰되었으며, 이 결과는 4L-hexagonal구조가 metal-metal 결합에 의해 안정화되어 있기 때문인 것으로 설명된다.

The Sr1-xYxMnO3 (x = 0.0∼1.0) system was synthesized using amorphous citrate process. The stability of various structures and the electronic transport properties of this system were investigated. X-ray diffraction study indicated that the Sr1-xYxMnO3 system has three different structures depending on composition, namely, 4L-hexagonal perovskite (when x is less than 0.3), pseudocubic perovskite (when x is 0.3∼0.7), and hexagonal nonperovskite (when x is larger than 0.7) structures. The structural changes and electronic properties were interpreted based on two factors, i.e., the size of cations and the oxidation state of manganese ion. When the concentration of Y substitution exceeds 30%, the Mn-Mn repulsive interaction dominates over intermetallic attraction, and thus structure changes to pseudocubic perovskite. In perovskite phase the unit cell dimensions increases with increasing Mn3+ ions due to yttrium substitution. The band gap of Sr0.9Y0.1MnO3 is greater than that of Sr0.5Y0.5MnO3. The greater band gap of Sr0.9Y0.1MnO3 indicates that the 4L-hexagonal structure is more stabilized than cubic perovskite due to the Mn-Mn bond.

785 - 791
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