Enhanced thermoelectric performance of p-type Bi0.5Sb1.5Te3 through Cu doping and zone melting

Thermoelectric (TE) materials enable direct thermal-electric energy conversion, but Bi 2 Te 3 -based alloys suffer from limited thermoelectric performance and controversial doping mechanisms of Cu, hindering their practical application in waste heat recovery. To address these issues, this work designs and synthesizes a series of zone-melted p-type Bi 0.5 Sb 1.5*(1− x ) Cu 1.5* x Te 3 +3 wt % Te ( x  = 0.0–2.0%) samples. The results show that Cu occupies interstitial sites, suppresses Te volatilization to increase the hole concentration, and enhances the electrical conductivity. Concurrently, lattice distortions and secondary phases reduced lattice thermal conductivity. The 1.0% Cu-doped sample achieves a maximum power factor of 4.74 mW·m − 1 ·K − 2 at 300 K, a peak zT of 1.03 at 412 K, and an average zT of 0.91 (300–500 K), representing improvements of 7%, 8.4%, and 18% over the undoped matrix. Subsequent hot deformation further reduced lattice thermal conductivity but did not enhance zT due to an anomalous rise in carrier concentration and decreased mobility. This study clarifies the interstitial Cu doping mechanism, providing a viable strategy for optimizing Bi 2 Te 3 -based materials.