Characterization and thermoelectric properties of Bi0.4Sb1.6Te3 nanostructured bulk prepared by mechanical alloying and microwave activated hot pressing

The p-type Bi0.4Sb1.6Te3 nanostructured bulk thermoelectric materials were obtained by mechanical alloying combined with a new consolidation technique of microwave activated hot pressing (MAHP). The effect of sintering temperature and holding time on the microstructure and thermoelectric properties of p-type Bi0.4Sb1.6Te3 bulks were investigated in detail. Compared with the traditional microwave pressureless sintering, the MAHP technique can be used to produce relatively compact bulks, caused by a uniaxial pressure. Due to the microwave arcing effect, the irregular shape nanograins are formed in situ in the MAHP samples. The coexistence of nano-sized grains and micro-sized grains can promote the effective scattering of phonons of a wide spectrum of wavelength and decrease the lattice thermal conductivity. A minimum lattice thermal conductivity of 0.41 W/(m K) and a maximum dimensionless figure of merit value of 1.13 were obtained for the MAHP sample sintered at 375 °C and 15 min. The MAHP technique introduced in this work can be extended to other ceramics to obtain fine microstructures at low sintering temperatures in a very short period of time.