A High-Pressure Polymorph of Troilite, FeS

Area of Science:

• Geochemistry
• Materials Science
• Mineral Physics

Background:

• Iron sulfide (FeS) exists in various polymorphs, with troilite being a common low-pressure form.
• Understanding FeS polymorphs is crucial for interpreting geological processes and material properties under extreme conditions.

Purpose of the Study:

• To synthesize and characterize a new polymorph of iron sulfide (FeS) at high pressures.
• To determine the stability and transition behavior of this novel FeS phase.

Main Methods:

• High-pressure synthesis using a diamond-anvil cell.
• Optical microscopy for observation.
• X-ray diffraction for analyzing structural properties and recording reflections.

Main Results:

• A new polymorph of FeS was successfully produced and stabilized at pressures above approximately 55 kilobars at 25 degrees C.
• Fourteen x-ray reflections were recorded for the high-pressure FeS, indicating a distinct crystalline structure, though its exact arrangement remains undetermined.
• The transition from the new high-pressure FeS polymorph back to troilite was observed to be rapid and reversible upon pressure release.

Conclusions:

• A previously unknown polymorph of FeS can be formed and stabilized under high-pressure conditions.
• The new FeS phase exhibits unique structural characteristics identifiable by x-ray diffraction.
• The reversible and rapid transition to troilite suggests potential implications for understanding phase transformations in FeS systems.