Thermal stability of FeSi as barrier layer in high-performance Mg2Si0.3Sn0.7 thermoelectric device

Thermal stability of thermoelectric devices plays a pivotal role in their practical applications. Chemical reaction/diffusion between thermoelectric materials and electrodes is one of the primary factors contributing to the degradation/failure of device performance at elevated temperatures. Introducing barrier layers to impede the behavior of chemical reactions has emerged as an effective approach for averting the failure of these devices. In this work, the FeSi is revealed to be a potent material of barrier layer in high-performance Mg 2 Si 0.3 Sn 0.7 thermoelectric material based on the considerations of interfacial reaction energy and sinterability. The well-established bond in Mg 2 Si 0.3 Sn 0.7 /FeSi joint results in a low contact resistivity of ∼20 μΩ⸱cm 2 and a conversion efficient of ∼6.5% for the Mg 2 Si 0.3 Sn 0.7 single-leg device is achieved at a temperature difference of ∼290 K. Long-term measurements of the device at a hot-side temperature of 600 K reveal that the performance remains nearly invariable as time further increases, which suggests that the FeSi layer retards the chemical reaction/diffusion. • FeSi was proposed as a barrier layer for Mg 2.03 (Si 0.3 Sn 0.7 ) 0.993 Bi 0.007 based on interfacial reaction energy. • The single-leg device of Mg 2.03 (Si 0.3 Sn 0.7 ) 0.993 Bi 0.007 /FeSi/Cu achieved a η max of 6.5% at Δ T ∼290 K. • Good thermal stability of the single-leg device was demonstrated by aging and long-term cycle testing.