Pressure-temperature stability studies of FeOOH using X-ray diffraction

Abstract

The Mie-Grüneisen formalism is used to fit a Birch-Murnaghan equation of state to high-temperature (T), high-pressure (P) x-ray diffraction unit-cell volume (V)

Pressure–volume–temperature equation of state of ε–FeOOH to 11 GPa and 700 K

“…The transformation from goethite to ε-FeOOH was observed in heating under high pressure at 600 K and 8.3 GPa. These conditions are very close to the phase boundary between α-and ε-FeOOH (Gleason et al, 2008). Because the transformation occurred at 600 K, the XRD study on the stable condition of α-FeOOH was limited to 400 K. XRD data were obtained with decreasing temperature and pressure.…”

“…Therefore, the study of the properties of δ-AlOOH, phase H, ε-FeOOH and their solid solution under high pressure and high temperature conditions is very important. An X-ray diffraction (XRD) study under high pressure and high temperature conditions was carried out by Gleason et al (2008). However, the pressure-volume-temperature (P-V-T ) equation of state (EOS) was not determined.…”

Pressure-Induced Hydrogen Bond Symmetrization in Iron Oxyhydroxide

“…[22]). This indicates that up to 16 GPa, similar to isostructural -AlOOH [23], bulk compression takes place through contraction of the channels, involving shortening of the hydrogen bonds, rather than slimming down of the FeO 6 octahedra [19]. At $16 GPa the compressibility of the O1-H Á Á Á O2 bond decreases sharply and becomes comparable to the compressibility of the Fe-O bonds (Fig.…”

“…Nagai et al [18] carried out powder XRD studies to 24 GPa and derived a bulk modulus K 0 ¼ 111ð2Þ GPa and its pressure derivative K 0 ¼ 4. Studies to 29 GPa by Gleason et al [19] deduced values of K 0 and K 0 of 140(4) and 4.6(4) GPa, respectively. The behavior of goethite under pressure has been studied theoretically by Otte…”

“…High pressure structural studies of goethite up to $29 GPa have been performed by several groups [18,19]. Nagai et al [18] carried out powder XRD studies to 24 GPa and derived a bulk modulus K 0 ¼ 111ð2Þ GPa and its pressure derivative K 0 ¼ 4.…”