Thermodynamic criterions of the thermoelectric performance enhancement in Mg2Sn through the self-compensation vacancy

Abstract We show a significant increase in thermoelectric figure-of-merit ZTmax from 0.7 of the normally doped Mg2Sn0.99Sb0.01 to 1.2 of the self-compensatively doped Mg1.94Sn0.8Sb0.2, which corresponds to a 70% enhancement. We provide a thermodynamic equilibrium energy criterion that explains the formation of compensation defects, and non-equilibrium transport criterion that is relative to the self-compensation defects to boost the thermoelectric performance, i.e. the normalized change of material parameter ΔB/Bpure. Based on the theoretical basis of alloying scattering related to the electrons and phonons, we discuss the analytical optimized fraction of the dopants or the self-compensation vacancy in two cases, respectively. Our work provides a new theoretical guideline for the design of novel thermoelectric materials through the defects engineering, especially the self-compensation defects.