Phase relations in the Fe-FeSi system at high pressures and temperatures
Phase relations in the Fe-FeSi system at high pressures and temperatures
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DOI：
10.1016/j.epsl.2013.04.035
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发表时间：
2013-07-01
影响因子：
5.3
通讯作者：
Prakapenka, Vitali B.
中科院分区：
文献类型：
--
作者：
Fischer, Rebecca A.;Campbell, Andrew J.;Prakapenka, Vitali B.
地球的核心主要由铁和镍组成，但它也含有几个重量百分比的一种或多种未知的轻元素，其中可能包括硅。因此，了解Fe-FeSi系合金的高压、高温性能和行为，如它们的相图是很重要的。我们确定的熔化温度和亚固相线相关系的Fe-9重量%的Si和化学计量的FeSi使用同步辐射X射线衍射在高压和高温下，高达类似于200 GPa和类似于145 GPa，分别。将这些数据与以前的研究相结合，我们生成了压力-温度，温度-组成和压力-组成空间的相图。我们发现在Fe-9 Si中的B2晶体结构，其中先前的研究报道了较不有序的bcc结构，并且hcp+B2到fcc+B2边界的斜率比先前报道的要小。在化学计量的FeSi中，我们报告了宽的B2+B20两相场，在类似于42 GPa下完全转化为B2结构。基于Fe-9 Si的共晶熔点，Fe-Si外芯的最低温度为4380 K，并且硅被示出在核心条件下比氧或硫在降低铁的熔点方面效率更低。在达到最高压力时，在Fe FeSi系统中仅观察到hcp和B2结构。我们预测，含有超过4- 8wt%硅的合金将转化为hcp+B2混合物，然后随着压力的增加转化为hcp结构，并且地球内核中的铁硅合金很可能是hcp和B2相的混合物。(C)2013爱思唯尔有限公司版权所有。
The Earth's core is comprised mostly of iron and nickel, but it also contains several weight percent of one or more unknown light elements, which may include silicon. Therefore it is important to understand the high pressure, high temperature properties and behavior of alloys in the Fe-FeSi system, such as their phase diagrams. We determined melting temperatures and subsolidus phase relations of Fe-9 wt% Si and stoichiometric FeSi using synchrotron X-ray diffraction at high pressures and temperatures, up to similar to 200 GPa and similar to 145 GPa, respectively. Combining this data with that of previous studies, we generated phase diagrams in pressure-temperature, temperature-composition, and pressure-composition space. We find the B2 crystal structure in Fe-9Si where previous studies reported the less ordered bcc structure, and a shallower slope for the hcp+B2 to fcc+B2 boundary than previously reported. In stoichiometric FeSi, we report a wide B2+B20 two-phase field, with complete conversion to the B2 structure at similar to 42 GPa. The minimum temperature of an Fe Si outer core is 4380 K, based on the eutectic melting point of Fe-9Si, and silicon is shown to be less efficient at depressing the melting point of iron at core conditions than oxygen or sulfur. At the highest pressures reached, only the hcp and B2 structures are seen in the Fe FeSi system. We predict that alloys containing more than similar to 4-8 wt% silicon will convert to an hcp+B2 mixture and later to the hcp structure with increasing pressure, and that an iron silicon alloy in the Earth's inner core would most likely be a mixture of hcp and B2 phases. (C) 2013 Elsevier B.V. All rights reserved.