Bulletin of the American Physical Society
22nd Biennial Conference of the APS Topical Group on Shock Compression of Condensed Matter
Volume 67, Number 8
Monday–Friday, July 11–15, 2022; Anaheim, California
Session W01: Phase Transitions in Non-Metals
4:00 PM–5:15 PM,
Thursday, July 14, 2022
Anaheim Marriott
Room: Platinum 5
Chair: Federica Coppari, Lawrence Livermore Natl Lab
Abstract: W01.00002 : In situ X-ray diffraction of Al2O3 during laser compression and release*
4:15 PM–4:30 PM
Presenter:
Anirudh Hari
(Johns Hopkins University)
Authors:
Anirudh Hari
(Johns Hopkins University)
Rohit Hari
(Johns Hopkins University)
Saransh Singh
(Lawrence Livermore Natl Lab)
Joel V Bernier
(Lawrence Livermore Natl Lab)
Raymond F Smith
(Lawrence Livermore Natl Lab)
Thomas S Duffy
(Princeton University)
Todd C Hufnagel
(Johns Hopkins University)
June K Wicks
(Johns Hopkins University)
Sapphire (Al2O3) is an important earth mineral notable for its high compressive strength and hardness. Static compression experiments on Al2O3 in the polycrystalline alumina form have found evidence of phase transformations from the α-corundum phase to a Rh2O3 (II)-type structure at ~80 GPa (Funamori & Jeanloz, 1997, Lin et al., 2004), and then to the post-perovskite structure at ~130 GPa (Oganov & Ono, 2005).
In this work, we describe laser-driven shock compression experiments on a-cut and c-cut sapphire to 150 GPa and polycrystalline alumina to 110 GPa conducted at the Matter in Extreme Conditions endstation of the Linac Coherent Light Source. Ultrafast x-ray pulses (50 fs, 1012 photons/pulse) were used to probe the lattice-level response as a function of time during and after shock propagation. VISAR velocimetry was used to measure free-surface particle velocity, from which pressure was calculated. Through in situ x-ray diffraction, we observe evidence of anisotropic strain and crystal break-up during and after compression. After release to ambient pressure, measured temperatures exceed those predicted by isentropic release, indicating plastic work heating. We will discuss the effect of crystal orientation on shock-induced phase transformation.
*This work was funded in part by DOE-NNSA SSAA grant DE-NA0003902. (PI: T. Hufnagel, co-PI: J. Wicks)
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