Engineering the Thermoelectric and Magnetocaloric Performance of Bi_0.4Sb_1.6Te₃–Cr₅Te₆ Composites

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 Bi0.4Sb1.6Te3–Cr5Te6 composites, where a spatially confined ferromagnetic Cr5Te6 phase is embedded into the Bi0.4Sb1.6Te3 thermoelectric matrix. The diffusion of Te element from Bi0.4Sb1.6Te3 into Cr5Te6 as a result of concentration gradient during sintering leads to the formation of interfacial phase Cr2Te3 and SbTe antisite defects in the Bi0.4Sb1.6Te3, 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 SbTe 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 ΔSmax = 0.33 J kg–1 K–1 at 5 T have been obtained for the Bi0.4Sb1.6Te3-15 wt % Cr5Te6 composite sintered at 625 K. This research offers a promising pathway for the development of high-performance magnetocaloric and thermoelectric composite materials.