High performance functionally graded and segmented Bi2Te3-based materials for thermoelectric power generation

Bi2Te3-based materials possess a figure of merit maximum over a narrow temperature range. When used in a generating mode over a large temperature difference the material operates at a substantially lower overall figure of merit than its maximum value. The conversion efficiency of a thermoelectric generator for low temperature waste heat recovery can be increased by employing functionally graded or segmented materials. In this work functionally graded p-type Bi2Te3-based thermoelectric materials have been prepared from melt by the Bridgman method using double doping technique. Segmented n-type thermoelement has been fabricated by joining two Bi2Te3-based materials with figure of merit maximum at 270 K and 380 K. The thermoelectric properties of the materials and a thermocouple comprised of p-type functionally graded and n-type segmented materials have been measured over a temperature range 200 K–450 K. The material efficiency of the thermocouple over the temperature gradient 223 K–423 K is estimated to be 10% compared with 8.8% for a standard Bi2Te3-based materials.