Optimization of Co additive amount to improve thermoelectric properties of <i>β</i> -FeSi ₂

Abstract The present manuscript deals with the synthesis of pure and Co-doped β -FeSi 2 by the conventional arc-melting method and the investigation of the effect of Co-dopant on the structural, electrical, and thermoelectric properties of β -Fe 1− x Co x Si 2 (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 μ Wm −1 K −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) × 10 20 cm −3 and mobility for 3.5(6) cm 2 V −1 s −1 , where the highest ZT is 0.099.

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