Magnesium silicide based materials are widely studied for thermoelectric power generation. They are very promising, non-toxic and light candidates with high ZT and ample availability of their constituent elements in nature. Ternary Mg2(Si,Sn) series has been found to be the most favorable, while more recent studies on the Si-rich members have also exhibited high ZT.
This presentation will review recent developments on the Si-rich Mg2(Si,Sn,Ge) series. These materials exhibit compositional variations, which extend from nanoscale to macroscale, with Sn-rich and Si-rich phases, as observed with HRTEM, SEM/EDX and IR-reflectivity mappings. These all-length-scale observations verified the presence of hierarchical structure extending down to a few nanometers. The introduction of Bi/Sb as well as Ge in the Si-sublattice modifies the existence of different compositions and their thermoelectric properties while phase separation is strongly stimulated by doping. The coexistence of different compositions seem to lead to high ZT, i.e. 1.4 at 800K.