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The high-pressure, high-temperature phase diagram of cerium

DOI: 10.1088/1361-648X/ab7f02 DOI Help

Authors: Keith Munro (The University of Edinburgh) , Dominik Daisenberger (Diamond Light Source) , Simon Macleod (Atomic Weapons Establishment) , Steve Mcguire (Atomic Weapons Establishment) , Ingo Loa (The University of Edinburgh) , Catalin Popescu (Synchrotron Light Facility, ALBA) , Pablo Botella (Lulea University of Technology) , Daniel Errandonea (Universidad de Valencia) , Malcolm Mcmahon (The University of Edinburgh)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Journal Of Physics: Condensed Matter

State: Published (Approved)
Published: March 2020
Diamond Proposal Number(s): 9548 , 7533

Open Access Open Access

Abstract: We present an experimental study of the high-pressure, high-temperature behaviour of cerium up to $\sim$22 GPa and 820 K using angle-dispersive x-ray diffraction and external resistive heating. Studies above 820 K were prevented by chemical reactions between the samples and the diamond anvils of the pressure cells. We unambiguously measure the stability region of the orthorhombic \textit{oC}4 phase and find it reaches its apex at 7.1 GPa and 650 K. We locate the $\alpha$-\textit{cF}4 -- \textit{oC}4 -- \textit{tI}2 triple point at 6.1 GPa and 640 K, 1 GPa below the location of the apex of the \textit{oC}4 phase, and 1-2 GPa lower than previously reported. We find the $\alpha$-\textit{cF}4 $\rightarrow$ \textit{tI}2 phase boundary to have a positive gradient of 280 K/GPa, less steep than the 670 K/GPa reported previously, and find the \textit{oC}4 $\rightarrow$ \textit{tI}2 phase boundary to lie at higher temperatures than previously found. We also find variations as large as 2-3 GPa in the transition pressures at which the \textit{oC}4 $\rightarrow$ \textit{tI}2 transition takes place at a given temperature, the reasons for which remain unclear. Finally, we find no evidence that the $\alpha$-\textit{cF}4 $\rightarrow$ \textit{tI}2 is not second order at all temperatures up to 820 K.

Subject Areas: Physics

Instruments: I15-Extreme Conditions