Experimental Evidence for Partially Dehydrogenated ε-FeOOH

Zhuang, Yongyong; Cui, Zhongxun; Zhang, Dongzhou; Liu, Jin; Tao, Renbiao; Hu, Qingyang

doi:10.3390/cryst9070356

Cited by 5 publications

(4 citation statements)

References 42 publications

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“…This is previously regarded as a symbol of anisotropy of the charge carrier transportation in the crystallites 40 . While both our x-ray diffraction experiment and literature data indicate that ε-FeOOH is a stable phase throughout the pressure range we have investigated 27,41,42 , the appearance of the second arc coincides with the spin-paring of Fe 42 . The spin transition of Fe may create grain boundaries between the high-spin and low-spin domains.…”

Section: Resultssupporting

confidence: 53%

Metallized ε-FeOOH and the heterogeneous electrical conductivity structure in the lower mantle

Zhuang

Cui

Tang

et al. 2020

Preprint

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Electrical heterogeneity at the depth of 900-1400 km in Earth’s interior is a key factor to constrain the minor phase composition of the lower mantle. However, prevailing mineralogical models including Fe- or Al-enriched silicates or ferropericlase are insufficient to explain the ultra-high electrical conductivity in local areas of subduction slabs. Here, we measure the electrical conductivity of ε-FeOOH up to 61 GPa. A 3-order abrupt jump of electrical conductivity is observed in 45-50 GPa, reaching 1.24±0.19 × 103 S/m at 61 GPa. Density mean field theory simulations suggest that ε-FeOOH undergoes a Mott-type electronic transition, which leads the conduction mechanism to switch from small polaron conduction to free electron conduction. Compared with bridgmanite, ferropericlase and conventional mantle compositional models, the electrical conductivity of the metallic ε-FeOOH is 1-3 orders of magnitude higher. Minor or moderate incorporation of metallic ε-FeOOH into the ambient lower mantle could reproduce the observed electrical heterogeneity derived from geomagnetic data at 900-1400 km depth.

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Section: Resultssupporting

confidence: 53%

Metallized ε-FeOOH and the heterogeneous electrical conductivity structure in the lower mantle

Zhuang

Cui

Tang

et al. 2020

Preprint

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“…DOI: https://doi.org/10.2138/am-2021-7541. http://www.minsocam.org/ slowly increases with increasing FeOOH content (Gleason et al, 2013;Hsieh et al, 2020;Ohira et al, 2019;Thompson et al, 2020;Zhuang et al, 2019). It has been proposed that ferropericlase (Mg,Fe)O and ferromagnesite (Mg,Fe)CO would uptake more iron when entering the low spin state in the lower mantle (Cerantola et al, 2017;Lobanov et al, 2015).…”

Section: Discussionmentioning

confidence: 99%

“…On the other hand, the spin transition pressure of the Delta52 phase is between 41 and 45 GPa via the laser Raman experiment using neon as a pressure-transmitting medium in this study. The spin crossover of Delta52 is 3-5 GPa lower than that of ε-FeOOH by XRD experiments using the same pressure-transmitting medium (Thompson et al, 2020;Zhuang et al, 2019). It should be mentioned that Gleason et al (2013) reported that the spin crossover of ε-FeOOH is much wider…”

Section: The Effect Of Feooh Content On the Spin Transition Of δ-(Almentioning

confidence: 93%

“…Such anomalies may contribute to a local thermal abnormal conductivity at depths approximately from 800 to 1400 km (Hsieh et al, 2020). However, most of the previous studies on δ-(Al,Fe)OOH are limited to its end-members and a low FeOOH content in δ-(Al,Fe)OOH (0≤Fe/(Fe+Al)≤0.15) (Duan et al, 2018;Gleason et al, 2013;Hsieh et al, 2020;Mashino et al, 2016;Ohira et al, 2019;Su et al, 2020;Zhuang et al, 2019). Knowledge of how the incorporation of Fe 3+ affects the behavior of δ-AlOOH at high pressure is still rather scanty.…”

Section: Introductionmentioning

confidence: 99%

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Spectroscopic evidence for the Fe3+ spin transition in iron-bearing δ-AlOOH at high pressure

Zhao

et al. 2021

American Mineralogist

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δ-AlOOH has emerged as a promising candidate for water storage in the lower mantle and could have delivered water into the bottom of the mantle. To date, it still remains unclear how the presence of iron affects its elastic, rheological, vibrational, and transport properties, especially across the spin crossover. Here, we conducted high-pressure X-ray emission spectroscopy experiments on a δ-(Al0.85Fe0.15) OOH sample up to 53 GPa using silicone oil as the pressure transmitting medium in a diamond-anvil cell. We also carried out laser Raman measurements on δ-(Al0.85Fe0.15)OOH and δ-(Al0.52Fe0.48)OOH up to 57 and 62 GPa, respectively, using neon as the pressure-transmitting medium. Evolution of Raman spectra of δ-(Al0.85Fe0.15)OOH with pressure shows two new bands at 226 and 632 cm−1 at 6.0 GPa, in agreement with the transition from an ordered (P21nm) to a disordered hydrogen bonding structure (Pnnm) for δ-AlOOH. Similarly, the two new Raman bands at 155 and 539 cm−1 appear in δ-(Al0.52Fe0.48)OOH between 8.5 and 15.8 GPa, indicating that the incorporation of 48 mol% FeOOH could postpone the order-disorder transition upon compression. On the other hand, the satellite peak (Kβ′) intensity of δ-(Al0.85Fe0.15)OOH starts to decrease at ~30 GPa and it disappears completely at 42 GPa. That is, δ-(Al0.85Fe0.15)OOH undergoes a gradual electronic spin-pairing transition at 30–42 GPa. Furthermore, the pressure dependence of Raman shifts of δ-(Al0.85Fe0.15)OOH discontinuously decreases at 32–37 GPa, suggesting that the improved hydrostaticity by the use of neon pressure medium could lead to a relatively narrow spin crossover. Notably, the pressure dependence of Raman shifts and optical color of δ-(Al0.52Fe0.48)OOH dramatically change at 41–45 GPa, suggesting that it probably undergoes a relatively sharp spin transition in the neon pressure medium. Together with literature data on the solid solutions between δ-AlOOH and ε-FeOOH, we found that the onset pressure of the spin transition in δ-(Al,Fe)OOH increases with increasing FeOOH content. These results shed new insights into the effects of iron on the structural evolution and vibrational properties of δ-AlOOH. The presence of FeOOH in δ-AlOOH can substantially influence its high-pressure behavior and stability at the deep mantle conditions and play an important role in the deep-water cycle.

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Deep mantle hydrogen in the pyrite-type FeO2–FeO2H system

2021

Geoscience Frontiers

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Experimental Evidence for Partially Dehydrogenated ε-FeOOH

Cited by 5 publications

References 42 publications

Metallized ε-FeOOH and the heterogeneous electrical conductivity structure in the lower mantle

Metallized ε-FeOOH and the heterogeneous electrical conductivity structure in the lower mantle

Spectroscopic evidence for the Fe3+ spin transition in iron-bearing δ-AlOOH at high pressure

Deep mantle hydrogen in the pyrite-type FeO2–FeO2H system

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