Investigation of skutterudite MgyCo4Sb12: High pressure synthesis and thermoelectric properties

The filling behavior of Mg atoms into CoSb3 lattice voids under pressure was investigated theoretically, revealing ambient-pressure-inaccessible Mg-filled CoSb3 can be stabilized under high pressure. Inspired by this result, we synthesized Mg-filled CoSb3 using high pressure synthesis. The synthetic samples show Im3¯ symmetry of skutterudite structure, with Mg filling fraction as high as 0.4. Thermoelectric measurements indicated a significant reduction in thermal conductivity and a limited enhancement of power factor after Mg filling, which may connect with the relatively high electronegativity of Mg. The highest ZT of 0.33 was achieved in Mg0.4Co4Sb12 at 620 K. Compared with the traditional solid state reaction method, high pressure synthesis can substantially shorten the reaction duration and extend fillable elements, thus providing us an effective pathway for thermoelectric materials fabrication.