A new high-pressure polymorph of Ti2O3: implication for high-pressure phase transition in sesquioxides
A new high-pressure polymorph of Ti2O3: implication for high-pressure phase transition in sesquioxides
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DOI：
10.1080/08957950802665747
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发表时间：
2009-08
影响因子：
2
通讯作者：
D. Nishio–Hamane;M. Katagiri;K. Niwa;A. Sano‐Furukawa;T. Okada;T. Yagi
中科院分区：
文献类型：
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作者：
D. Nishio–Hamane;M. Katagiri;K. Niwa;A. Sano‐Furukawa;T. Okada;T. Yagi
用金刚石对顶砧同步辐射X射线衍射和透射电镜研究了Ti_2O_3的后晶相变。在约19 GPa和1850 K下发现了新的Ti 2 O3多晶型物，并且该相即使在约40 GPa下也是稳定的。在Pnma正交晶胞上对一种新的Ti_2O_3多晶型进行了表征，其晶胞参数为：a=7.6965（19）μ m，B=2.8009（9）μ m，c=7.9300（23）μ m，V=170.95（15）μ m ~ 3，a=7.8240（2）μ m，B=2.8502（1）μ m，c=8.1209（3）μ m，环境条件下V=181.10（1）Ω 3。Birch-Murnaghan状态方程计算结果表明，在α相，K 0=206（3）GPa，K′0=4（固定）;在α相后，K 0=296（4）GPa，K′0=4（固定）。在约20 GPa的相变中，摩尔体积减小了12%。用Rietveld方法对回收的样品进行了结构鉴定，发现一种新的Ti_2O_3晶型为Th_2S_3型而不是U_2S_3型结构。从刚玉型到Th_2S_3型的转变伴随着多面体形态的急剧变化：从刚玉型的TiO_6八面体到Th_2S_3型的TiO_7多面体。
The post-corundum phase transition has been investigated in Ti2O3 on the basis of synchrotron X-ray diffraction in a diamond anvil cell and transmission electron microscopy. The new polymorph of Ti2O3 was found at about 19 GPa and 1850 K, and this phase was stable even at about 40 GPa. A new polymorph of Ti2O3 can be indexed on a Pnma orthorhombic cell, and the unit-cell parameters are a=7.6965 (19) Å, b=2.8009 (9) Å, c=7.9300 (23) Å, V=170.95 (15) Å3 at 19 GPa, and a=7.8240 (2) Å, b=2.8502 (1) Å, c=8.1209 (3) Å, V=181.10 (1) Å3 at ambient conditions. The Birch–Murnaghan equation of state yields K 0=206 (3) GPa and K′0=4 (fixed) for corundum phase, and K 0=296 (4) GPa and K′0=4 (fixed) for the post-corundum phase. The molar volume decreases by 12% across the phase transition at around 20 GPa. The structural identification was carried out on a recovered sample by the Rietveld method, and a new polymorph of Ti2O3 can be identified as Th2S3-type rather than U2S3-type structure. The transition from corundum-type to Th2S3-type structure accompanies the drastic change of the form of polyhedron: from TiO6 octahedron in the corundum-type to TiO7 polyhedron in the Th2S3-type structures.