Improving n-type thermoelectric performance of Mg2Si0.4Sn0.6 compounds via high pressure and Sb-doping

n-type Mg 2 (Si 0.4 Sn 0.6 ) 1- x Sb x compounds were synthesized using high-pressure techniques followed by spark plasma sintering. Structural and compositional analyses revealed a predominant anti-fluorite phase with minimized oxidation and volatilization of Mg, leading to improved thermoelectric properties in our samples. This study highlights the controllable nature of composition, distribution, and fraction of in-situ nanostructures through specific high-pressure synthesis conditions and spark plasma sintering. X-ray diffraction, backscattered images, and Scanning transmission electron microscopy results showed that the nanoprecipitates consist of a solid solution phase of Mg 2 Sn and Mg 2 Si with varying compositions. The Mg 2 (Si 0.4 Sn 0.6 ) 0.98 Sb 0.02 sample has the lowest lattice thermal conductivity, 1.14 Wm- 1 K-1 at room temperature and 0.53 Wm- 1 K-1 at 623 K. The optimal Mg 2 (Si 0.4 Sn 0.6 ) 0.98 Sb 0.015 composition demonstrated the highest power factor and lowest thermal conductivity, resulting in a peak ZT value of 1.48 at 823 K. The decrease in thermal conductivity, along with a thorough comprehension of the microstructural elements responsible for this decrease, can offer valuable insights and guidance for advancing thermoelectric materials with a high thermoelectric figure of merit. Our findings highlight the benefits of utilizing high pressure in the synthesis of Mg 2 Si-based thermoelectric materials to improve their thermoelectric performance.