Thermoelectric properties of Cu-doped n-type (Bi2Te3)0.9–(Bi2−xCuxSe3)0.1(x=0–0.2) alloys

n-Type (Bi2Te3)0.9–(Bi2−xCuxSe3)0.1 (x=0–0.2) alloys with Cu substitution for Bi were prepared by spark plasma-sintering technique and their structural and thermoelectric properties were evaluated. Rietveld analysis reveals that approximate 9.0% of Bi atomic sites are occupied by Cu atoms and less than 4.0 wt% second phase Cu2.86Te2 precipitated in the Cu-doped parent alloys. Measurements show that an introduction of a small amount of Cu (x⩽0.1) can reduce the lattice thermal conductivity (κL), and improve the electrical conductivity and Seebeck coefficient. An optimal dimensionless figure of merit (ZT) value of 0.98 is obtained for x=0.1 at 417 K, which is obviously higher than those of Cu-free Bi2Se0.3Te2.7 (ZT=0.66) and Ag-doped alloys (ZT=0.86) prepared by the same technologies.