Pressure induced Fe2++Ti4+ ? Fe3++Ti3+ intervalence charge transfer and the Fe3+/Fe2+ ratio in natural ilmenite (FeTiO3) minerals
Pressure induced Fe2++Ti4+ ? Fe3++Ti3+ intervalence charge transfer and the Fe3+/Fe2+ ratio in natural ilmenite (FeTiO3) minerals
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DOI：
10.1088/0953-8984/16/15/021
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发表时间：
2004-04
期刊：
影响因子：
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通讯作者：
T. Seda;G. Hearne
中科院分区：
文献类型：
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作者：
T. Seda;G. Hearne
天然钛铁矿（FeTiO_3）样品中Fe ~（3+）/Fe ~（2+）比值在压力从常压到GPa的范围内迅速增大。该比率在环境压力下最初为0.2，在超过2-4 GPa时饱和，在本研究中达到最高压力14 GPa。显著的变化发生在低压下，其中单位晶胞的可压缩性是明显各向异性的，c轴比a轴更可压缩，并且与在压力下观察到的电阻的快速降低一致。压力引起的价间电荷转移远离亚铁位点，可以想象的是穿过八面体的区域，到沿着c轴沿着相邻面共享层中的Ti 4+阳离子的空的3d流形可以解释Fe 3 +/Fe 2+比率的变化。
The Fe3+/Fe2+ ratioin natural ilmenite (FeTiO3) samples shows rapid increase under pressure from ambient up to GPa, as deduced from 57Fe Mossbauer pressure studies. The ratio, which is initially 0.2 at ambient pressure, saturates at beyond 2–4 GPa to the highest pressure of 14 GPa in this study. Dramatic changes occur at low pressure where the compressibility of the unit cell is appreciably anisotropic, the c-axis being more compressible than the a-axis, and coincides with the rapid decrease observed in the electrical resistance under pressure. Pressure induced intervalence charge transfer away from the ferrous sites, conceivably across regions of octahedra, to the empty 3d manifold of the Ti4+ cation in an adjacent face-sharing layer along the c-axis may account for the change in the Fe3+/Fe2+ ratio.