Does Low‐Level Substitution Aid in Improving Thermoelectric Properties? A Case Study of M _0.1 Ni _0.9 Cr ₂ S ₄ (M = Mn, In)

The influence of low-level metal cation substitution in the thermoelectric material NiCr2S4, treated via field-assisted sintering, is investigated X-ray diffraction (XRD) and transmission electron microscopy (TEM) studies. NiCr2S4 Mn0.1Ni0.9Cr2S4 can be synthesized compacted as phase-pure pellets, while In0.1Ni0.9Cr2S4 appears a mixture different phases. XRD investigations reveal that Mn incorporated into host material's Ni lattice sites, In mainly additional Both form structure chemically segregated, nanoscale domains, which appear significantly more pronounced for Mn0.1Ni0.9Cr2S4. All materials exhibit similar, promising thermal conductivities around 2.0 W m−1 K−1, with Seebeck coefficients ranging from −55 to −65 μV K−1. Only electrical conductivity noticeably influenced by substitutions, highest value 504 S cm−1 obtained pristine material, subsequently declining both substituted