Pressure-induced structural and electronic transitions of thiospinel Fe₃S₄

Abstract

We report the investigations on the structural and electronic properties of an inverse spinel Fe3S4 at high pressures using synchrotron x-ray diffraction (XRD) and electrical transport measurements. Our XRD measurements at high pressures reveal an irreversible structural phase transformation on compression above ∼3 GPa from a cubic spinel (Fd-3m space group) into a monoclinic Cr3S4-type structure (I2/m space group). Electrical transport measurements suggest that the high pressure monoclinic phase has a semiconducting behavior. This semiconducting behavior is found to persist up to the highest pressure of measurement of ∼23 GPa. These results show that while Fe3S4 possesses similar high pressure structural properties with other thiospinels, the electronic properties under pressure show a rather strong similarity to its oxide counterpart, Fe3O4, at high pressures.

Greigite (Fe 3 S 4 ) is thermodynamically stable: Implications for its terrestrial and planetary occurrence

“…We have confirmed the existence of the high-pressure monoclinic Fe 3 S 4 phase (13)(14)(15), which is supposed to be ferrimagnetic like the cubic spinel (13,15). We synthesized the material at 5 GPa and ambient temperature in a multianvil press to investigate its structure and thermodynamics (Fig.…”

“…Greigite transforms from a cubic spinel structure to a monoclinic Cr 3 S 4 -type structure at 3-4 GPa (13,14). A natural nanosized monoclinic Fe 3 S 4 phase, probably the same as the reported highpressure phase, has been found in the Sudbury ore deposit (15).…”

“…Although relatively low, this resistivity is higher than for a typical metal. This complex resistivity behavior is attributed to the enhancement of electron hopping between Fe 2+ and Fe 3+ ions mediated by polarons (14). The mobility of polarons is increased by compression.…”

“…The enthalpy of transition from greigite to the high-pressure phase, measured by oxide melt solution calorimetry, is endothermic: 14.1 ± 8.3 kJ/mol per FeS 1.33 formula unit, and the change in molar volume is −10.46 ± 0.22 cm 3 mol −1 . According to Susilo et al (14), the high-pressure monoclinic phase starts appearing above 3 GPa at ambient temperature and the cubic phase is completely transformed to the monoclinic phase at 6 GPa. The transition has not been reversed.…”

“…Monoclinic Fe 3 S 4 was predicted to undergo a half-metal to metallic transition upon compression (13), but electrical transport measurements showed only semiconducting behavior in the highpressure phase (14), The experimental studies have indeed shown a drop in resistivity to 4-6 mΩcm upon compression above 2 GPa. Although relatively low, this resistivity is higher than for a typical metal.…”