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

Abstract Atomic disordering was an effective strategy to reduce lattice thermal conductivity. In this work, the atomic disordering of Mg2-δSn1-xBix was maximized by both the charge self-compensation and steric effects. Due to the strong phonon scattering arose from substitutional defects BiSn and self-compensational vacancies VMg, an exclusively low lattice thermal conductivity of 1.38 W m−1 K−1 was observed in the Mg2-δSn0.8Bi0.2 sample, corresponding to only 30% of Mg2Sn, while a 30% less than that of its counterpart Mg2-δSn0.8Sb0.2 (1.97 W m−1 K−1). The EPMA result presents that the Mg2-δSn0.8Bi0.2 has a higher concentration of VMg than that of Mg2-δSn0.8Sb0.2, suggesting an apparent steric effect for the formation of VMg. 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 Mg2-δSn0.8Bi0.2 sample, which is 52% higher than the conventionally doped Mg2Sn0.99Bi0.01, while comparable with the Mg2-δSn0.8Sb0.2. This work provides new insight into tuning thermoelectric transport properties through the atomic disorder strategy.