Enhanced thermoelectric performance of p-type Bi0.5Sb1.5Te3 through incorporation of ferromagnetic spinel CuCr2Se4

Bismuth telluride and its alloys remain the most promising near-room-temperature thermoelectric materials, driving continued research efforts for performance optimization. Recent advances have demonstrated that incorporating magnetic secondary phases as functional units can effectively enhance thermoelectric properties via the paradigm-changing mechanisms from the additional spin-orbital degrees of freedom. In this work, micron-scale ferromagnetic spinel CuCr 2 Se 4 particles were strategically introduced into a p-type Bi 0.5 Sb 1.5 Te 3 matrix through hot-pressing sintering to create Bi 0.5 Sb 1.5 Te 3 - x wt% CuCr 2 Se 4 composites. Systematic characterization revealed a notable improvement in the power factor along with a significant reduction in lattice thermal conductivity in the composites. The improvement in electrical performance is derived from an optimized carrier concentration, achieved through the carrier injection driven by the work-function difference between the matrix and the secondary phase. Meanwhile, an increase in the Seebeck coefficient can be associated with the magnetic phase transition of magnetic second phase. The reduction in thermal conductivity stems from the additional magnon–phonon scattering introduced by the incorporation of the ferromagnetic CuCr 2 Se 4 secondary phase. The optimized composite achieved a maximum figure of merit zT of 1.30 at 375 K and an exceptional average zT of 1.15 over the temperature range of 300 ∼ 500 K. These findings underscore that the strategic integration of magnetic CuCr 2 Se 4 as a secondary phase in p-type Bi 0.5 Sb 1.5 Te 3 can concurrently improve electronic transport and suppress thermal conduction, offering a viable pathway for developing high-performance thermoelectric materials.