Optimizing Room‐Temperature Thermoelectric and Magnetocaloric Performance via Constructing Multi‐Scale Interfacial Phases in LaFeSi/BiSbTe Thermo‐Electro‐Magnetic Refrigeration Materials

Abstract Fabricating a thermo‐electro‐magnetic material that exhibits simultaneously excellent magnetocaloric (MC) and thermoelectric (TE) performance is challenging since the interfacial reaction causes severe deterioration of MC and TE performance. In this work, a construction of multi‐scale interfaces in LaFe 10.4 Co 0.8 Si 1.8 /Bi 0.5 Sb 1.5 Te 3 (LFS/BST) composites is realized by adopting a low‐temperature high‐pressure sintering strategy. It is revealed in the atomic‐scale that the interfacial reaction between LFS and BST leads to the formation of (Fe,Co)(Sb,Te) 2 micro‐grains and LaTe 2 nano‐grains, and the latter form low‐mismatch phase boundaries with LFS matrix. Benefiting from the multi‐scale interfacial phases, excellent MC performance of LFS is preserved alongside a minor impact on TE properties, e.g., a peak zT of 1.04 and a small decrease of 3.0% in relative cooling power are achieved in the 2%LFS/BST composite. Compared with other thermo‐electro‐magnetic materials, a good trade‐off between MC and TE performance is realized in LFS/BST composites with simultaneously high MC and TE performance. The 20%LFS/BST composite exhibits a room‐temperature zT of 0.46 with large maximum magnetic entropy change and relative cooling power of 0.81 J kg −1 K −1 and 44.83 J kg −1 , respectively. This work provides an effective material design for developing the all‐solid‐state MC/TE hybrid refrigeration technique.