Valence Transitions in Negative Thermal Expansion Material SrCu3Fe4O12

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• 作者：Ikuya Yamada ; Kentaro Shiro ; Hidenobu Etani ; Shohei Marukawa ; Naoaki Hayashi ; Masaichiro Mizumaki ; Yoshihiro Kusano ; Shigenori Ueda ; Hideki Abe ; Tetsuo Irifune
• 刊名：Inorganic Chemistry
• 出版年：2014
• 出版时间：October 6, 2014
• 年：2014
• 卷：53
• 期：19
• 页码：10563-10569
• 全文大小：480K
• ISSN：1520-510X

文摘

The valence states of a negative thermal expansion material, SrCu₃Fe₄O₁₂, are investigated by X-ray absorption and ⁵⁷Fe M枚ssbauer spectroscopy. Spectroscopic analyses reveal that the appropriate ionic model of this compound at room temperature is Sr²⁺Cu^鈭?.4+₃Fe^鈭?.7+₄O₁₂. The valence states continuously transform to Sr²⁺Cu^鈭?.8+₃Fe^鈭?.4+₄O₁₂ upon cooling to 鈭?00 K, followed by a charge disproportionation transition into the Sr²⁺Cu^鈭?.8+₃Fe³⁺_鈭?.2Fe⁵⁺_鈭?.8O₁₂ valence state at 鈭? K. These observations have established the charge-transfer mechanism in this compound, and the electronic phase transitions in SrCu₃Fe₄O₁₂ can be distinguished from the first-order charge-transfer phase transitions (3Cu²⁺ + 4Fe^3.75+ 鈫?3Cu³⁺ + 4Fe³⁺) in Ln³⁺Cu²⁺₃Fe^3.75+₄O₁₂ (Ln = trivalent lanthanide ions).