Thermoelectric Characteristics of p-Type (Bi,Sb)(2)Te-3/(Pb,Sn)Te Functional Gradient Materials with Variation of the Segment Ratio

Abstract

The p-type (Bi,Sb)(2)Te-3/(Pb,Sn)Te functional gradient materials (FGMs) were fabricated by hot-pressing mechanically alloyed (Bi0.2Sb0.8)(2)Te-3 and 0.5 at.% Na2Te-doped (Pb0.7Sn0.3)Te powders together at 500A degrees C for 1 h in vacuum. Segment ratios of (Bi,Sb)(2)Te-3 to (Pb,Sn)Te were varied as 3:1, 1.3:1, and 1:1.6. A reaction layer of about 350-mu m thickness was formed at the (Bi,Sb)(2)Te-3/(Pb,Sn)Te FGM interface. Under temperature differences larger than 340A degrees C applied across a specimen, superior figures of merit were predicted for the (Bi,Sb)(2)Te-3/(Pb,Sn)Te FGMs to those of (Bi0.2Sb0.8)(2)Te-3 and (Pb0.7Sn0.3)Te. With a temperature difference of 320A degrees C applied across a specimen, the (Bi,Sb)(2)Te-3/(Pb,Sn)Te FGMs with segment ratios of 3:1 and 1.3:1 exhibited the maximum output powers of 72.1 mW and 72.6 mW, respectively, larger than the 63.9 mW of (Bi0.2Sb0.8)(2)Te-3 and the 26 mW of 0.5 at.% Na2Te-doped (Pb0.7Sn0.3)Te.