Optimum composition of a Bi2Te3 − x Se x alloy for the n-type leg of a thermoelectric generator

Abstract

The reliability of determination of model parameters for the Bi2Te3 − xSex alloys is improved by extending the concentration and temperature ranges in experimental studies and, correspondingly, in calculations of kinetic coefficients based on the two-band model of the electronic spectrum. The obtained results served as a motivation for a study of the thermoelectric figure of merit for the above-mentioned alloys with x = 0.3, 0.45, and 0.6 and with the electron concentration varied in the range (1–50) × 1018 cm−3 at temperatures 300–550 K. Comparison of the results showed that the highest efficiency is exhibited by the Bi2Te2.7Se0.3 alloy with the absolute value of the thermoelectric power of about 165 μVK−1 at 300 K, and the dimensionless efficiency is equal to 1.2 at 410 K. An appreciable decrease in thermal conductivity in alloys with x = 0.6 at 410 K is related to a larger band gap and could beneficially affect the figure of merit. However, the magnitude of this effect is found to be too small to compensate a decrease in electrical conductivity due to a large fraction of heavy electrons in the concentration and to a high content of selenium.