Study of iron oxides under laser-driven shock compression

Céline Crépisson [webpage]

Department of Physics, Clarendon Laboratory, University of Oxford 

Amphi A

ABSTRACT

Iron oxides are of significance within the Earth lower mantle. They are present both as a major (Mg,Fe)O phase or within subducted material such as Banded Iron Formations (with the presence of FeOOH, Fe₂O₃, Fe₃O₄). Their electronic and structural properties under pressure could explain seismological heterogeneities in the lower mantle [1] and Ultra-Low Velocity Zones at the Core Mantle Boundary [2]. Moreover, iron oxides melts can provide information on the Fe-O bonding environment within the Earth’s outer-core of possible interest for the Geodynamo [3]. Laser-driven shock compression probed by an X-ray Free Electron Laser makes it possible to access the high-pressure regime of Earth’s lower mantle and outer-core, and to study the evolution of both electronic and structural properties of iron oxides. In this talk I will present results on Fe₂O₃ and FeO using in-situ x-ray diffraction (XRD) under laser-driven shock compression up to 209 GPa. Electronic and structural evolutions of Fe₂O₃ and FeO at lower-mantle pressures under shock are compared to previous static compression data. The behaviour of Fe₂O₃ above 122 GPa, shown to undergo amorphization and melting, is reported for the first time. I will also present some preliminary work looking at accessing directly the electronic structure of FeO (via Resonant Inelastic X-ray Scattering) and FeO elastic constants (via XRD) under pressure.  

REFERENCES 

[1] Lin et al., Science 317, (2007) 

[2] Dobson et al., Nature 434, (2005) 

[3] Ozawa et al., Science 334, (2011)