Synthesis and thermoelectric properties of Cu excess Cu₂ZnSnSe₄

Quaternary stannites with an excess of copper were successfully synthesized by reacting the constituent elements and subsequent solid state annealing, followed by densification by hot-pressing. The composition for each specimen was confirmed with a combination of Rietveld refinement and elemental analysis. Their high temperature thermoelectric properties were measured from 300 K to 800 K and compared with that of Cu₂ZnSnSe₄. The thermal conductivity decreases significantly with increasing Cu content at elevated temperatures due to the crystal structure of this material system. A maximum ZT value of 0.86 was obtained at 800 K for the specimen with the highest Cu content, Cu_2.2Zn_0.8SnSe₄.