Structure-property relationships in pyrochlores: low-temperature structures of Tl2Ru2O7-δ (δ=0.00 and 0.05)
Structure-property relationships in pyrochlores: low-temperature structures of Tl2Ru2O7-δ (δ=0.00 and 0.05)
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烧绿石的结构-性质关系：Tl2Ru2O7-δ（δ=0.00 和 0.05）的低温结构
DOI：
10.1039/a805664a
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发表时间：
1999
影响因子：
--
通讯作者：
A. Hewat
中科院分区：
文献类型：
--
作者：
T. Takeda;R. Kanno;Y. Kawamoto;M. Takano;F. Izumi;A. Sleight;A. Hewat
研究了焦绿钌的结构、电学和磁性能。研究了焦绿盐钌铊的结构
Structural, electrical and magnetic properties are investigated for ruthenium pyrochlores. The structure of the thallium ruthenium pyrochlore, Tl
2
Ru
2
O
7–δ
, has been determined for δ=0.00 and 0.05 by neutron diffraction measurements at low temperatures. Stoichiometric Tl
2
Ru
2
O
7.00
synthesized under a high oxygen pressure of 3 GPa using KClO
4
shows a first-order metallic-semiconducting transition at 120 K. The high-temperature metallic phase has a cubic pyrochlore structure with a three dimensional network of both ruthenium fand thallium. The low-temperature semiconducting phase has thallium sites with slightly short and long Tl-O distances, and the two Tl sites are ordered one dimensionally in the orthorhombic cell. Charge disproportionation of the Tl ions was suggested by valence bond sum calculations. By contrast, non-stoichiometric Tl
2
Ru
2
O
6.95
showed a spin-glass-like or canted-spin behavior around 40 K with resistivity increase also observed at this temperature. No significant structure changes were observed at the transition. Metallic-semiconducting transitions are discussed on the basis of their bond distance and angle changes.