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Chemical substitution, Indium thiospinel, Solid solution, Thermoelectric properties
Abstract:
Crystal structure as well as magnetic and thermoelectric properties of the quaternary Fe1-xMnxIn2S4 thiospinel were investigated. A complete homogeneity range between FeIn2S4 and MnIn2S4 was confirmed by powder X-ray diffraction phase analysis supported by a linear increase of the cubic unit-cell parameter for greater Mn content, obeying Vegard's law. Rietveld refinement revealed a gradual decrease of the inversion parameter i upon incorporation of Mn into the structure, which indicated a change from inverse spinel (for FeIn2S4) to nearly-normal spinel (for MnIn2S4). This quaternary compound is an n-type semiconductor with high electrical resistivity ρ > 5 × 10−4 Ω m and Seebeck coefficient |α| > 250 μV K−1 above RT. The thermal conductivity followed a compositional dependence typical for solid solutions and thus revealed a minimum for samples with 0.4 < x ≤ 0.8. The power factor and thermoelectric figure of merit monotonously decreased for greater Mn content within the quaternary compound. All samples showed magnetic transitions below 12 K with antiferromagnetic interactions. The determined effective magnetic moments corresponded to values for Fe2+ and Mn2+ ions. © 2021 Elsevier Ltd
