Maximized atomic disordering approach boost the thermoelectric performance of Mg2Sn through the self-compensation effect and steric effect

Atomic disordering was an effective strategy to reduce lattice thermal conductivity. In this work, the atomic disordering of MgSnBi was maximized by both the charge self-compensation and steric effects. Due to the strong phonon scattering arose from substitutional defects Bi and self-compensational vacancies V, an exclusively low lattice thermal conductivity of 1.38 W m K was observed in the MgSnBi sample, corresponding to only 30% of MgSn, while a 30% less than that of its counterpart MgSnSb (1.97 W m K). The EPMA result presents that the MgSnBi has a higher concentration of V than that of MgSnSb, suggesting an apparent steric effect for the formation of V. Furthermore, the Mg vacancy and its induced lattice shrinkage also result in band convergence. Consequently, a high ZT of 1.14 was obtained at 500 °C in the MgSnBi sample, which is 52% higher than the conventionally doped MgSnBi, while comparable with the MgSnSb. This work provides new insight into tuning thermoelectric transport properties through the atomic disorder strategy.