Enhanced thermoelectric properties of n-type Bi2Te2.7Se0.3 by indium and sodium co-doping

Abstract

Bi (1.98-x) In 0.02 Na x Te 2.7 Se 0.3 (x = 0, 0.02, 0.04, 0.06) and Bi 2 Te 2.7 Se 0.3 alloys were prepared by vacuum melting and hot pressing methods. The phase structure of the bulk samples were characterized by X-ray diffraction. Effects of indium and sodium co-substitutions for bismuth on the electrical and thermal transport properties were investigated in the temperature range of 298–473 K. Indium and sodium co-doping can enhance the carrier concentration, and accordingly the electrical conductivity can be improved effectively. The Seebeck coefficients of the co-doped samples have not been derogated strongly. The power factors are enhanced for the Bi (1.98-x) In 0.02 Na x Te 2.7 Se 0.3 (x = 0.02) within the whole testing temperature range. The Bi (1.98-x) In 0.02 Na x Te 2.7 Se 0.3 (x = 0.02) samples have the lower thermal conductivity due to reduction in lattice thermal conductivity, which leads to a great improvement in the thermoelectric figure of merit ZT. The highest ZT of the sample can reach 0.87 at 398 K.