Mg _(2) X ~(IV) (X ~(IV) = Si, Ge, Sn) compounds are semiconductors and their solid solutions are believed to be promising mid-temperature thermoelectric materials. By contrast, Mg _(2) Pb is a metal and few studies have been conducted to investigate the thermoelectric properties of Mg _(2) Si–Mg _(2) Pb solid solutions. Here, we present a theoretical study exploring whether Mg _(2) Pb–Mg _(2) Si solid solutions can be used as thermoelectric materials or not. We firstly constructed several Mg _(2) Si _(1? x ) Pb _( x ) (0 ≤ x ≤ 1) structures and calculated their electronic structures. It is suggested that Mg _(2) Si _(1? x ) Pb _( x ) are potential thermoelectric semiconductors in the range of 0 ≤ x ≤ 0.25. We then explicitly computed the electron relaxation time and both the electronic and lattice thermal conductivities of Mg _(2) Si _(1? x ) Pb _( x ) (0 ≤ x ≤ 0.25) and studied the effect of Pb concentration on the Seebeck coefficient, electrical conductivity, thermal conductivity, and thermoelectric figure of merit ( ZT ). At low Pb concentration ( x = 1/16), the ZT of the Mg _(2) Si _(1? x ) Pb _( x ) solid solutions (up to 0.67 at 900 K) reaches a maximum and is much higher than that of Mg _(2) Si.
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