Enhanced Thermoelectric Performance of Ni x Bi0.5Sb1.5Te3 via In Situ Formation of NiTe2 Channels

In an endeavor to develop high figure of merit (ZT) thermoelectric materials for power generation and cooling applications, the in situ nano-inclusion formation led to improvement in thermoelectric performance. Herein, we studied the controlled Ni inclusion in the Bi0.5Sb1.5Te3 (BST) matrix with varying Ni concentrations, that is, Ni x Bi0.5Sb1.5Te3 (x = 0, 0.01, 0.04, and 0.08). Structural and microscopic analyses showed a clear formation of multi-structured p-type Bi0.5Sb1.5Te3 with fine channels of NiTe2 and their interface, which forms a potential barrier of 0.26 eV, giving rise to a carrier filtering effect. The inclusion of optimized Ni concentration, that is, x = 0.04, in Ni x Bi0.5Sb1.5Te3 and formation of NiTe2 channels has resulted in higher electrical conductivity of 900 S/cm and Seebeck coefficient of 210 μV/K simultaneously as compared to pristine BST. Further, Ni0.04Bi0.5Sb1.5Te3 has exhibited a ZT value of 1.4 at 373 K, which is 112% higher than the ZT (∼0.66 @ 373 K) of pristine BST.