In-situ X-ray diffraction study on β-CrOOH at high pressure and high-temperature

ABSTRACT

High pressure hydrous phases with distorted rutile-type structure have attracted much interest as potential water reservoirs in the Earth’s mantle. An in-situ X-ray diffraction study of β-CrOOH was performed at high pressures of up to 6.2 GPa and high-temperatures of up to 700 K in order to clarify the temperature effect on compression behaviors of β-CrOOH. The P-V-T data fitted to a Birch–Murnaghan equation of state yielded the following results: isothermal bulk modulus K_T0 = 191(4) GPa, temperature derivative (∂K_T/∂T)_P = −0.04(2) GPa K⁻¹, and volumetric thermal expansion coefficient α = 3.3(2) × 10⁻⁵ K⁻¹. In this study, at 300 K, the a-axis became less compressible at pressures above 1–2 GPa. We found that the pressure where the slopes of a/b and a/c ratios turned positive increased with temperature. This is the first experimental study indicating the temperature dependence of the change in the axial compressibility in distorted rutile-type M³⁺OOH.

KEYWORDS:

• β-CrOOH
• Birch–Murnaghan equation of state
• X-ray diffraction
• hydrogen bond

Acknowledgements

The authors are thankful to K. Obata and F. Maeda for their technical support with sample synthesis and to Y. Hirano for his help with the analysis of results. The synchrotron X-ray diffraction experiments at the beamline AR-NE5C were performed with the approval of the Photon Factory Advisory Committee [Proposal number 2018G023].

Disclosure statement

No potential conflict of interest was reported by the authors.

ORCID

Kazuhiro Fuchizaki http://orcid.org/0000-0001-6215-9867

Additional information

Funding

This work was supported by Ministry of Education, Culture, Sports, Science and Technology [grant number JP15H05828].