In situ high-pressure study of LiNbO₃-type FeTiO₃: X-ray diffraction and Mössbauer spectroscopy

Abstract

The structure of LiNbO₃-type FeTiO₃ and the oxidation state of Fe have been investigated using X-ray diffraction and Mössbauer spectroscopy in the diamond anvil cell up to 18 GPa at room temperature. A structural phase transition is observed at 15.7 GPa from LiNbO₃-type to perovskite-type, accompanied by a volume collapse of 1.5%. LiNbO₃-type FeTiO₃, which is shown to contain only ferrous iron up to this pressure, and no charge transfer is observed. In addition to the c/a axial ratio that has been used to distinguish between ilmenite and LiNbO₃-type FeTiO₃, the hyperfine parameters (isomer shift and quadrupole splitting) provide an efficient way to discriminate between these two phases.

Keywords:

• LiNbO₃-type structure
• phase transition
• Mössbauer spectroscopy
• ilmenite

Acknowledgements

X. Wu is grateful for the support from the Alexander von Humboldt Foundation and the financial support of the National Natural Science Foundation of China (Grant no. 40972029).