Enhanced thermoelectric performance of bismuth-doped magnesium silicide synthesized under high pressure
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Polycrystalline Mg2Si1−xBi x compounds were prepared with high-pressure synthesis followed by spark plasma sintering. The structural and compositional analyses indicate a dominant antifluorite phase with the oxidation and volatilizing loss of Mg highly suppressed. High-pressure synthesis promotes Bi doping and the formation of interstitial Mg, both of which contribute electrons and give rise to high carrier concentration. Meanwhile, a relatively high carrier mobility is maintained with elevating carrier concentration, beneficial to the thermoelectric properties enhancement of our high-pressure synthesized samples. The optimal Mg2Si0.985Bi0.015 possesses the highest power factor and the lowest thermal conductivity. As a result, the maximal ZT of 0.98 is achieved at 883 K, one of the highest values for the Bi-doped binary Mg2Si compounds. Our results thus indicate the advantage of high pressure in synthesizing Mg2Si-based thermoelectric materials with enhanced thermoelectric performance.
This work was supported by the Natural Science Foundation of China (51525205, 51421091, 51402254, and 51722209) and the Key Basic Research Project of Hebei (14961013D).
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