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Free keywords:
FeGa3, substitution, solid solution, electron and phonon engineering, thermoelectric properties
Abstract:
In this study we performed substitution experiments on the gallium site of the intermetallic semiconductor FeGa3, to adjust the charge carrier concentration, and determined the thermoelectric (TE) properties of the resulting products. Isoelectronic species aluminium and indium, hole-doping zinc, and electron-doping germanium were chosen to find suitable substituent elements. The samples FeGa3−x E x (E = Al, In, Zn, Ge; x = 0.03, 0.05, 0.06, 0.10, 0.20) were prepared by liquid–solid–reaction with subsequent spark plasma sintering treatment. X-ray diffraction, metallographic, and microstructure analysis were used to determine chemical composition and to evaluate the suitability of the substitution element. For solid solutions FeGa3−x Al x and FeGa3−x In x the substitution concentrations were very low (x ≤ 0.02) and did not improve the TE properties of FeGa3. The samples FeGa3−x Zn x had the expected p-type behaviour and slightly lower thermal conductivity than the binary compound. A substantial increase in the TE figure of merit was achieved for the solid solution FeGa3−x Ge x for which transition from semiconducting to metal-like behaviour was observed, with an additional decrease of thermal conductivity. The maximum ZT value of 0.21 was achieved for the composition FeGa2.80Ge0.20.
