Microstructure and transport properties of copper-doped p-type BiSbTe alloy prepared by mechanical alloying and subsequent spark plasma sintering

Effect of Cu-doping on the microstructure and transport properties of p-type thermoelectric BiSbTe alloy is studied. Quaternary Cu-Bi-Sb-Te alloys with general formula of CuxBi0.5−xSb1.5Te3 (x = 0, 0.04, 0.07, 0.1) are prepared by mechanical alloying and spark plasma sintering. The results show that the doping of copper has significant effect on the microstructure of the samples. With x increasing up to 0.07, the alloys begin to present an especial microstructure which consists of fault structure and dispersed pores. The electrical conductivities of the specimens are obviously improved to 1.9 × 105 S m−1 which is about 35% higher than the maximum value observed in pure Bi0.5Sb1.5Te3 alloy by far. The maximum power factor value of 1.9 × 10−3 W m−1 K−2 is obtained for the Cu0.1Bi0.4Sb1.5Te3 alloy between 325 and 450 K, being approximately twice as large as those of ternary Bi0.5Sb1.5Te3 alloy obtained in our work around the temperature at which the maximum power factor is achieved. Nano-scale dispersed pores in Cu0.07Bi0.43Sb1.5Te3 and Cu0.1Bi0.4Sb1.5Te3 alloy have significant effect on the reduction of lattice thermal conductivity. ZT of 1.39 can be obtained for Bi0.5Sb1.5Te3 alloy at 390 K.