Miscibility gap and thermoelectric properties of ecofriendly Mg2Si1-xSnx (0.1 ≤ x ≤ 0.8) solid solutions by flux method

Mg2Si1-xSnx compounds are promising as environmentally friendly thermoelectric (TE) materials. For years, investigations of the TE properties of these compounds have been hindered by the poor reproducibility in sample preparation. In this work, we used a recently developed simple B2O3 flux method to prepare Mg2Si1-xSnx compounds over a wide composition range (0.1 <= x <= 0.8). The phase structure, microstructure, and TE properties have been investigated. We found that a miscibility gap existed at 0.2 <= x <= 0.45, substantially lower than the more generally accepted values 0.4 <= x <= 0.6, and a low lattice thermal conductivity of 1.4 W.m(-1) . K-1 in undoped Mg2Si0.55Sn0.45, which led to a ZT similar to 0.3 at 550 K. These results constitute a solid basis for investigating further optimization of the Mg2Si1-xSnx-based TE materials via doping and possibly nanostrucuring approaches.