Anion concentrations have been shown to have large impacts on the properties of materials. This is seen in systems where changes in stoichiometry result in emergent properties, such as superconductivity and metal-insulator transitions. Metal-insulator transitions have been observed in dichalcogenide compounds, such as NiS2 and NiSe2, where anion concentration are controlled through anion mixing. This site mixing leads to a breakdown in ordering that disrupts magnetism and band gaps causing antiferromagnetic insulators to transform into paramagnetic metals. Anion concentration also plays a large role in cuprate superconductors, such as YBa2Cu3Oy. The parent compound YBa2Cu3O6 is an antiferromagnetic Mott-insulator, but as oxygen is removed from the system the antiferromagnetic state is suppressed and superconductivity emerges. The Fe-Ga-S system allows the study of how anion concentrations can affect emergent properties in ternary compounds. This system provides multiple layered antiferromagnetic ternary phases which can be synthesized with a range of sulfur content. In this study, the phases FeGa2S4 and Fe2Ga2S5 are investigated. Both phases are layered antiferromagnetic compounds where FeGa2S4 contains a single layer of iron octahedra separated by gallium tetrahedra, and Fe2Ga2S5 contains a double layer of edge-shared iron octahedra. By using in-situ x-ray diffraction, the lattice parameters of these phases can be monitored throughout the reduction process. The contraction of the unit cell can be correlated with changes in lattice site occupancies giving insight into how the compounds are reduced. Once the reduction process is characterized, samples are made with varying anion concentrations. Material properties, such as electronic transport and magnetism, are measured to investigate how properties change as a function of anion content. A better understanding of how anion concentration affects material properties in the Fe-Ga-S system will help to build methods of studying reduction reactions as well as give insight into how electronic transport is affected by reduction conditions.

In-situ reduction study of the effect of anion concentration in the Fe-Ga-S system

253rd National Meeting (2017)

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