Improving Thermoelectric Performance of n-Type Mg₃Bi₂-Based Materials by Introducing a Spatially Confined Magnetic Ordered Structure

Magnetism, which relates to the spin and orbital degreesof freedom,is recently considered as the fountain of some potentially paradigm-changingmechanisms to decouple the adversely interdependent thermal and electricaltransport parameters of thermoelectric materials. Herein, we constructa thermo-electro-magnetic coupling thermoelectric system by introducinga spatially confined ferromagnetic CrTe secondary phase into the Mg3.4Bi1.5Sb0.5 (MBA) matrix. It is foundthat the spatially confined magnetic ordered structure, CrTe, canact as electron injection units to substantially promote the carrierconcentration of the MBA matrix without deteriorating the carriermobility, which usually occurs in the uniform magnetic-element dopingsystems. An increase in the Seebeck coefficient of the CrTe-incorporatedsystem due to the magnetic phase transition was also acknowledged,which further confirms the advantage of introducing spin and orbitaldegrees of freedom into the thermoelectric materials. Combined withthe enhanced phonon scattering by the second phase, a maximum zT value & SIM;1.1 was achieved in the 0.35 wt % CrTe/Mg3.4Bi1.5Sb0.5 composite at 587 K.