Synthesis and transport properties of [Ni3Sn][Ni4−xS2], an n-type metal-rich sulfide with an intergrowth structure

Abstract

By optimizing the synthetic route, a nearly 100% pure Ni₆SnS₂ polycrystalline dense sample was obtained. While the average crystal structure is consistent with the tetragonal I4/mmm symmetry, electron diffraction tomography analysis reveals a lower local symmetry accompanied by weak satellite reflections, indicative of structural modulation at the local scale for this metal-rich layered sulfide. This allowed the Ni₆SnS₂ transport properties to be studied. Despite its metal-like behavior with ρ = 0.16 mΩ cm at 300 K, the material exhibits a moderate thermal conductivity at 250 K (11.4 W m⁻¹ K⁻¹). Interestingly, its thermoelectric power factor (PF = S²/ρ = 0.32 mW m⁻¹ K⁻²) exceeds typical values observed in metallic materials.