Investigation of PdTe2 Phase Segregation on Thermoelectric Properties of n-Type Bi₂Te_2.7Se_0.3 Fabricated by Melt-Spinning Technique for Possible Carrier Filtering Effect

Influence of secondary phases of PdTe₂ in n-type thermoelectric Cu_0.008Bi₂Te_2.7Se_0.3 alloys on their thermoelectric properties was investigated through in situ phase separation by melt spinning process. The phase segregation of PdTe₂ in the Cu_0.008Bi₂Te_2.7Se_0.3 matrix were successfully induced by using the melt spinning process. Since heterointerfaces of PdTe₂ and Cu_0.008Bi₂Te_2.7Se_0.3 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 Cu_0.008Bi₂Te_2.7Se_0.3 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 Cu_0.008Bi₂Te_2.7Se_0.3 samples. This implies that the favorable carrier filtering effect could be attained by further controlling the optimal carrier concentration even with small barrier heights. Graphic Abstract: [Figure not available: see fulltext.]