Engineering the Thermoelectric and Magnetocaloric Performance of Bi0.4Sb1.6Te3–Cr5Te6 Composites

Abstract

Materials with both excellent magnetocaloric properties and high thermoelectric performance play a vital role in the invention of next-generation all-solid-state refrigeration technology. Herein, we investigate the interfacial reactions, thermoelectric and magnetocaloric properties of spark plasma sintered Bi_0.4Sb_1.6Te₃–Cr₅Te₆ composites, where a spatially confined ferromagnetic Cr₅Te₆ phase is embedded into the Bi_0.4Sb_1.6Te₃ thermoelectric matrix. The diffusion of Te element from Bi_0.4Sb_1.6Te₃ into Cr₅Te₆ as a result of concentration gradient during sintering leads to the formation of interfacial phase Cr₂Te₃ and Sb_Te antisite defects in the Bi_0.4Sb_1.6Te₃, both of which are detrimental to the thermoelectric and magnetocaloric performance of the composites. Sintering at a lower temperature effectively mitigates the interfacial reactions and suppresses Sb_Te antisite defects. Consequently, the room-temperature magnetocaloric and thermoelectric properties of the composites are concurrently optimized. Specifically, a high ZT value of 0.65 at 300 K and a relatively large magnetic entropy change ΔS_max = 0.33 J kg^–1 K^–1 at 5 T have been obtained for the Bi_0.4Sb_1.6Te₃-15 wt % Cr₅Te₆ composite sintered at 625 K. This research offers a promising pathway for the development of high-performance magnetocaloric and thermoelectric composite materials.