Structural and optical studies of FeSb2 under high pressure

TL;DR

This study investigates how high pressure affects the structural and optical properties of FeSb2, revealing phase stability, amorphous phase formation, and Raman mode changes up to 45 GPa.

Contribution

It provides detailed experimental data on FeSb2's structural phases and optical responses under high pressure, including phase transitions and Raman spectroscopy insights.

Findings

Orthorhombic FeSb2 remains stable up to 28.2 GPa.

Amorphous phase increases with pressure, reaching 23.3 GPa.

Raman mode disappears at 16.6 GPa, indicating phase change.

Abstract

Nanostructured orthorhombic FeSb2 and an amorphous phase were formed by mechanical alloying starting from a mixture of high purity elemental Fe and Sb powders. The effects of high pressures on structural and optical properties were studied using X-ray diffraction (XRD) and Raman spectroscopy (RS). XRD patterns showed the presence of the orthorhombic FeSb2 phase up to the maximum pressure applied (28.2 GPa). The XRD patterns showed also an increase in the amount of the amorphous phase with increasing pressure up to 23.3 GPa. At 14.3 GPa, together with the former phases, a new phase was observed and indexed to a tetragonal FeSb2 phase, but its volume fraction is small at least up to 23.3 GPa. For the orthorhombic FeSb2 phase, the pressure dependence of the volume fitted to a Birch-Murnaghan equation of state gave a bulk modulus = 74.2 +- 3.0 GPa and its pressure derivative = 7.5 +- 0.6. RS measurements were performed from atmospheric pressure up to 45.2 GPa. For the orthorhombic FeSb2 phase, the Raman active mode was observed up to the maximum pressure applied, while the mode disappeared at 16.6 GPa. For pressures higher than 21 GPa, the Raman active mode of a tetragonal FeSb2 phase was observed, confirming ab initio calculations reported in the literature.