The Effect of Porosity and Milling Induced Defects on the Thermoelectric Properties of p-Type Bi2Te3-Based Bulks

The p-type (Bi,Sb)(2)Te-3 bulks are prepared from ball-milling powders by resistance pressure sintering method and their thermoelectric properties are investigated as a function of ball milling time. Prolonging milling time would introduce more anti-site defects, interaction of vacancies and antisite defect, grain-boundaries and interface defects, leading to lower carrier concentration and mobility. The peak value of ZT = 1.0 is achieved at 300 K for the 5 h sample. When the testing temperature is over 323 K, the ZT value of the 0 h sample is higher than that of the 5 h sample. The effect of porosity on the thermoelectric properties is also investigated by effective medium theory. As the porosity increased, the electrical resistivity increases and the thermal conductivity decrease.