Electronic Materials Letters Investigation of PdTe2 Phase Segregation on Thermoelectric Properties of n-Type -Bi2Te2.7Se0.3 Fabricated by Melt-Spinning Technique for Possible Carrier Filtering Effect

Abstract

Influence of secondary phases of PdTe2 in n-type thermoelectric Cu0.008Bi2Te2.7Se0.3 alloys on their thermoelectric properties was investigated through in situ phase separation by melt spinning process. The phase segregation of PdTe2 in the Cu0.008Bi2Te2.7Se0.3 matrix were successfully induced by using the melt spinning process. Since heterointerfaces of PdTe2 and Cu0.008Bi2Te2.7Se0.3 form potential barriers, low energy carrier filtering effect could be expected; however, the power factor and effective mass decreased with the PdTe2 addition, which implies that the carrier filtering effect did not occur. The potential barrier of 0.06 eV expected at the interfaces between PdTe2 and Cu0.008Bi2Te2.7Se0.3 matrix seems not to induce carrier energy filtering effect. However, further investigation based on single parabolic band model shows that the non-degenerate mobility and quality factor B are enhanced by PdTe2 addition, suggesting that the further optimization of the carrier concentration would increase zT further in PdTe2-added Cu0.008Bi2Te2.7Se0.3 samples. This implies that the favorable carrier filtering effect could be attained by further controlling the optimal carrier concentration even with small barrier heights.