Role of Copper Doping in Modulating the Thermoelectric Properties of Eu ₁₁ Zn ₄ Sn ₂ As ₁₂

Layered Zintl phase materials are of great interest due to their directional bonding and electronic properties. Eu11Zn4Sn2As12 is a p-type semiconductor that has been proposed to undergo 3D-to-2D electronic transport as the carrier concentration increases. This commensurately modulated structure in space group R3¯m has been shown to improve its thermoelectric properties upon Na doping, concurrently decreasing electrical resistivity while maintaining a large Seebeck coefficient. In this study, Eu11Zn4Sn2As12 was doped with Cu with the goal of substituting in the [Zn2As3]5− defect hexagonal layers to improve electrical transport. Resistivity decreased from ∼5900 mΩ cm to ∼30 mΩ cm as the carrier concentration increased, and degenerate semiconductor behavior was observed in some doped samples. A maximum zT600K of 0.24 for x = 0.6 was reached.