Decoupling electronic transport properties: A combined physical and chemical pressure approach for boosting thermoelectric performance in skutterudites

Decoupling the interdependence between the Seebeck coefficient and electrical conductivity represents one of the primary challenges in optimizing thermoelectric materials. While pressure has been recognized as a powerful tool for modifying the properties of materials, the combination of physical and chemical pressure as a strategy to enhance thermoelectric performance has not been explored yet. Our investigation reveals that the impact of hydrostatic pressure on pristine CoSb 3 induces an increase in the band gap and a direct-to-indirect band transition around 6 GPa, significantly enhancing the Seebeck coefficient ( S ). Concomitantly, pressure decreases the electrical conductivity and increases the lattice thermal conductivity, reducing the thermoelectric figure of merit z T . A way to increase thermoelectric efficiency is to combine chemical pressure, via Ca-filling, with physical pressure in Ca-filled CoSb 3 . This new strategy results in a remarkable enhancement of the power factor, attributed to an increase in both S and electrical conductivity. Indeed, the substantial boost in the power factor effectively compensates for the pressure-induced increase in lattice thermal conductivity, resulting in a net improvement of z T . • Pressure-induced enhancement of S in CoSb 3 is linked to lowering of σ and increasing κ l . • Electronic interactions dominate the strain effects of metallic guest atoms in CoSb 3 . • The combination of physical and chemical pressure decouples the quantities involved in z T . • Ca@CoSb 3 at moderate pressure and temperature shows z T values above 1.