Phase transitions in praseodymium up to 23 GPa: An x-ray powder diffraction study
Phase transitions in praseodymium up to 23 GPa: An x-ray powder diffraction study
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DOI：
10.1103/physrevb.80.134105
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发表时间：
2009-10-01
影响因子：
3.7
通讯作者：
McMahon, M. I.
中科院分区：
文献类型：
--
作者：
Evans, S. R.;Loa, I.;McMahon, M. I.
镧系金属Pr已经通过X射线粉末衍射从5到23 GPa进行了研究，目的是解决长期存在的关于该元素的高压相，过渡和结构的身份的分歧。我们发现在7.4GPa以上观察到的畸变fcc（d-fcc）相具有Hamaya等人先前报道的菱面体hR 24结构，并且可以明确地排除其他作者提出的单斜结构。在13.7 GPa下，d-fcc相开始转变为另一相Pr-VII，其结构是体心斜方晶或其非常轻微的畸变。Pr-VII在20.5（5）GPa下转变为α-铀相。除了确定相变和结构，我们还解决了以前的衍射研究之间的许多分歧，并表明几乎所有以前的工作都与本研究一致。Pr-VII相可能存在于第二个镧系元素Nd中，这表明它可能是在镧系元素中观察到的相序列的额外成员。
The lanthanide metal Pr has been studied by x-ray powder diffraction from 5 to 23 GPa with the aim of resolving the long-standing disagreements about the identity of the high-pressure phases, transitions, and structures of this element. We find that the distorted-fcc (d-fcc) phase observed above 7.4 GPa has the rhombohedral hR24 structure reported previously by Hamaya et al. and can definitely rule out the monoclinic structure proposed by other authors. At 13.7 GPa, the d-fcc phase starts to transform to another phase, Pr-VII, the structure of which is body-centered orthorhombic or a very slight distortion thereof. Pr-VII transforms to the alpha-uranium phase at 20.5(5) GPa. In addition to identifying the phase transitions and structures, we have also resolved many of the disagreements between previous diffraction studies and show that almost all previous work is in agreement with the present study. The likely existence of the Pr-VII phase in a second lanthanide, Nd, suggests that it might be an additional member of the sequence of phases observed across the lanthanide elements.