Structural and optical studies of FeSb2 under high pressure

Nanostructured orthorhombic FeSb2 was formed along with an amorphous phase, by mechanical alloying from a mixture of Fe and Sb powders. The influence of pressure on the structural and optical properties of the material was investigated by X-ray diffraction (XRD) and Raman spectroscopy (RS) up to 28.2 and 45.2 GPa, respectively. The volume fraction of the amorphous phase increased with increasing pressure. For pressures above 14.3 GPa, a tetragonal FeSb2 phase was also observed. For the orthorhombic FeSb2 phase, the pressure dependence of the volume fitted to a Birch-Murnaghan equation of state gave a bulk modulus B0=75.5±3.2 GPa, and its derivative B0′=7.2±0.7. For the orthorhombic FeSb2 phase, the Raman active Ag2 mode was observed up to 28.3 GPa, while the B1g2 mode was not for pressures larger than 14 GPa. For pressures above 21 GPa, the Raman active A1g mode of a tetragonal FeSb2 phase was observed.