Improved thermoelectric properties of Mg2SixGeySn1-x-y nanoparticle-in-alloy materials

We theoretically find that introducing nanoparticles into Mg2SixGeySn1-x-y alloys considerably improves their thermoelectric figure of merit (ZT). We have computed the thermal conductivity versus nanoparticle size of this class of nanocomposites for nine different material types at various temperatures. We provide validity ranges of nanoparticle concentration that will not reduce the thermoelectric power factor, but will considerably decrease the thermal conductivity. ZT enhancements of two times the alloy values are within reach. In particular, n-type Mg2Si0.4Sn0.6 with Mg2Si or Mg2Ge nanoparticles stand out as one of the best materials for intermediate temperature (800 K) applications, providing a good nontoxic alternative to PbTe.