Growth Mechanism and Stability Study on the Fe3S4 Nanocrystals Synthesized Under Thermal and Humid Conditions

Greigite (Fe3S4) is important magnetic mineral that can not only instruct reducing environment but also provide paleomagnetic signal for the paleoenvironment research. Generally Fe3S4 exists as an unstable intermediate, whose preparation condition is rigorous. Previous studies have accumulated rich results, but the research on its stable conditions, formation mechanism, and evolution process remains to be verified. This study simulates the mineral growth and carries out experimental research systematically under thermal and humid conditions. Pure Fe3S4 is synthesized under the conditions of 200 °C, t = 30 h, pH = 4–5. The morphology of Fe3S4 is nanoscale particles. Fe3S4 stably exists at 200 °C, t = 30 h, and transforms to FeS2 with increasing time. The experimental results broaden the stability range of Fe3S4 in the Fe–S binary phase diagram. This study has typomorphic significance on geological conditions and provides a scientific basis for the preparation of Fe3S4 nano-magnetic materials.