The present manuscript deals with the synthesis of pure and Co-doped β-FeSi2 by conventional arc-melting method and the investigation of the effect of Co-dopant on the structural, electrical, and thermoelectric properties of β-Fe1-xCoxSi2 (0 ≤ x ≤ 0.06) from 300 to 800 K. The electrical resistivity decreases with increasing Co-doping due to the increase in carrier concentration. The Seebeck coefficient of all Co-doping samples (0.005 ≤ x ≤ 0.06) is higher and more stable than that of x = 0 due to the absence of the bipolar effect. Therefore, the maximum power factor is around 900 μWm-1K-2 obtained in x = 0.03 from 720 to 800 K. The thermal conductivity also slightly decreases with increasing x. As a result, the optimum doping level is achieved in x = 0.03 with the carrier density around 1.2(4) × 1020 cm-3 and mobility for 3.5(6) cm2V-1s-1, where the highest ZT is 0.099.
A thermoelectric generator, as a solid-state device, is considered a potential candidate for recovering waste heat directly as electrical energy without any moving parts. However, thermoelectric materials limit the application of thermoelectric devices due to their high costs. Therefore, in this work, we attempt to improve the thermoelectric properties of a low-cost material, iron silicide, by optimizing the Ni doping level. The influence of Ni substitution on the structure and electrical and thermoelectric characteristics of bulk β-FexNi1−xSi2 (0 ≤ x ≤ 0.03) prepared by the conventional arc-melting method is investigated. The thermoelectric properties are reported over the temperature range of 80–800 K. At high temperatures, the Seebeck coefficients of Ni-substituted materials are higher and more uniform than that of the pristine material as a result of the reduced bipolar effect. The electrical resistivity decreases with increasing x owing to the increases in metallic ε-phase and carrier density. The ε-phase increases with Ni substitution, and solid solution limits of Ni in β-FeSi2 can be lower than 1%. The highest power factor of 200 μWm−1K−2 at 600 K is obtained for x = 0.001, resulting in the enhanced ZT value of 0.019 at 600 K.
Employing thermoelectric (TE) materials, which can directly convert heat into electricity, are a promising strategy for recovering industrial waste heat.
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