ICT2014 Abstracts

In the field of thermoelectrics, it is important to take sustainability into account since the overall ecological backpack for certain materials can be surprisingly high, especially for rare elements. Commonly used materials often contain such rare elements in the Earth’s crust, such as Te and Bi; thus using them in a wider range of TE applications – particularly at levels that could impact global energy use - is uncertain. Silicide compounds seem to be a more advantageous choice not only because of their ample availability in nature, but also because of their non-toxicity that is consistent with the priority for environment- and human- friendly technology. Among silicide compounds, Mg₂Si system seems to be the best with the ternary series Mg₂(Si,Sn) presenting high ZT. Although Sn-rich side exhibits higher ZT values, the Si-rich side of Mg₂(Si,Sn) series seems to be more appropriate for applications due to the lower density, rather higher melting points and higher strength. Interestingly, quaternary Mg₂(Si,Sn,Ge) systems have not attracted much attention apart from few exceptions. Very recently the high figure of merit of this system was reported where ZT reached 1.4 on the Bi-doped Si-rich Mg₂Si_1-x-ySn_xGe_y (x=0.4, y=0.05) material. 

This presentation will review recent developments on the Si-rich quaternary Mg₂(Si,Sn,Ge)-based Materials. These materials exhibit compositional inhomogeneities, which extend from nanoscale to macroscale, with Sn-rich and Si-rich phases, as observed with HRTEM (nanoscale), SEM studies and EDX (microscale) and IR Reflectivity mappings (macroscale). The introduction of Bi/Sb as well as Ge in the Si-sublattice modifies the inhomogeneties and the thermoelectric properties.