High-temperature Mössbauer study of Fe-substituted mullite
High-temperature Mössbauer study of Fe-substituted mullite
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Fe 取代莫来石的高温穆斯堡尔研究
DOI：
10.2138/am.2005.1689
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发表时间：
2005
影响因子：
3.1
通讯作者：
H. Schneider
中科院分区：
文献类型：
--
作者：
D. Mack;K. Becker;H. Schneider
在氮气气氛下，从室温到1200 ℃测量了Fe取代的3/2-莫来石（10.3wt%Fe_2O_3）的穆斯堡尔谱。一个Voigt型拟合的光谱线的形状，提出了基于三个非等效的Fe 3+环境A，B，和C的莫来石结构的假设。Fe 3+子光谱显示约1.1（A）、0.7（B）和1.3 mm/s（C）的四极分裂，其中在室温下，子光谱A和B的异构体位移约为0.3 mm/s，位点C的异构体位移约为0.1 mm/s。子光谱A和B归因于两个不同的Fe 3+八面体网站在莫来石配位，经历略有不同的四极相互作用;第三个网站被分配给离子在四面体配位。子光谱A被分配给具有TO 4四面体作为次近邻的铁-氧八面体，而子光谱B可以对应于具有TO 4和T* O 4四面体的铁-氧八面体，在它们附近具有相关的氧空位。三个子谱的四极分裂几乎与温度无关。异构体位移的温度依赖性符合密切的谐波固体在高温极限的预期。穆斯堡尔谱研究不支持莫来石中Fe的任何温度诱导再分布。
Abstract Mössbauer spectra of Fe-substituted 3/2-mullite (10.3 wt% Fe2O3) have been measured from room temperature up to 1200 °C under nitrogen atmosphere. A Voigt-type fit to the spectral line shape is proposed that is based on the assumption of three non-equivalent Fe3+ environments A, B, and C in the mullite structure. The Fe3+ subspectra display quadrupole splittings of about 1.1 (A), 0.7 (B), and 1.3 mm/s (C) where the isomer shifts at room temperature are about 0.3 mm/s for subspectra A and B and about 0.1 mm/s for site C. Subspectra A and B are attributed to two different Fe3+ octahedral sites in mullite coordination, experiencing slightly different quadrupolar interactions; the third site is assigned to ions in tetrahedral coordination. Subspectrum A is assigned to the iron-oxygen octahedra having TO4 tetrahedra as next nearest neighbors, while subspectrum B may correspond to iron-oxygen octahedra having TO4 and T*O4 tetrahedra with associated oxygen vacancies in their vicinity. The quadrupolar splittings of the three subspectra are found to be almost independent of temperature. The temperature dependences of the isomer shifts conform closely to those expected for a harmonic solid at the high-temperature limit. The Mössbauer study gives no support for any temperature-induced redistribution of Fe in mullite.