Synergistic modulation of the thermoelectric performance of melt-spun p-type Mg2Sn via Na2S and Si alloying

Abstract

Mg₂Sn, comprising low-cost, earth-abundant and environmentally friendly elements, is a promising candidate for thermoelectric applications in a medium temperature range. In contrast to the well-developed high-performance n-type Mg₂Sn materials, the thermoelectric performance of their p-type counterparts still remains much inferior. Herein, p-type Mg₂Sn-based materials with combined addition of Na₂S and Si have been rapidly synthesized via melt spinning and hot pressing toward enhanced thermoelectric performance from 300 K to 723 K. Detailed diffraction and microscopy characterization reveals that both Na₂S and Si are alloyed into Mg₂Sn, forming complete Mg₂Sn-based solid solutions. The compositional modification optimizes the carrier concentration and strengthens phonon scattering, resulting in a much-enhanced power factor of 1.8 mW m⁻¹ K⁻² at 673 K and a low total thermal conductivity of 2.0 W m⁻¹ K⁻¹ at 523 K. Finally, a peak zT value of ∼0.52 is reached in (Mg₂Sn_0.9Si_0.1)_0.93(Na₂S)_0.07 at 673 K, which is one of the highest values for p-type Mg₂Sn-based materials. This study provides an effective strategy for the synergistic modulation of electrical and thermal transport properties of p-type Mg₂Sn.