Structural and optical studies of FeSb2 under high pressure

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.Comment: 31 pages, 11 figures and 2 tables. Already submitted for publicatio

Discovery of FeBi2

“…However, these numbers are still useful as a first approximation of bonding distances in intermetallic compounds. The shortest Fe–Fe distances in FeBi 2 are those along the c -axis, 2.7107(3) Å, which is longer than the Fe–Fe distance found in high-pressure FeSb 2 (2.536 Å at 28.2 GPa), 13 but shorter than those featured in the Al 2 Cu-type compound FeZr 2 , 2.798(2) Å. 15 …”

“…A search of known binary structure types with this space group yielded the Al 2 Cu structure type, in which several iron binary compounds crystallize. 13−15 The new phase was well modeled with Rietveld refinement as FeBi 2 in the Al 2 Cu structure type, with lattice parameters of a = 6.3121(3) Å and c = 5.4211(4) Å (at 29.9(1) GPa). The early transition metal–antimonides, TiSb 2 16 and VSb 2 , 17,18 crystallize within the same Al 2 Cu structure type at ambient pressures, while CrSb 2 and FeSb 2 undergo a pressure-induced transition from the marcasite FeS 2 structure type into the Al 2 Cu structure type at pressures of 5.5 GPa 19 and 14.3 GPa, 13 respectively.…”

Prediction of superconducting iron–bismuth intermetallic compounds at high pressure

“…85 Two of above Pnnm compounds, CrSb 2 and FeSb 2 , have been shown experimentally to undergo a pressure-induced phase transition into the Al 2 Cu structure at around 5.5 GPa ( ref. 86 ) and 14.3 GPa, 87 respectively. While these structural transitions have also been confirmed computationally, 88 the transition pressure in FeSb 2 is slightly overestimated (38 GPa).…”

“…Iron pnictides were found to exhibit temperature or pressure induced transitions from semiconductor to metal, accompanied with strong magnetic fluctuations [97][98][99]. Although these compounds crystallize in the marcasite phase, theoretical result predicts that FeP 2 , FeAs 2 and FeSb 2 transform into the Al 2 Cu structure at pressures of above 108, 92 and 38 GPa, respectively [89], and experimental observations report that the phase transition in FeSb 2 indeed occurs at 14.3 GPa [87].…”

“…97 – 99 Although these compounds crystallize in the marcasite phase, theoretical result predicts that FeP 2 , FeAs 2 and FeSb 2 transform into the Al 2 Cu structure at pressures of above 108, 92 and 38 GPa, respectively, 89 and experimental observations report that the phase transition in FeSb 2 indeed occurs at 14.3 GPa. 87 …”