Control of interfacial reaction and defect formation in Gd/Bi2Te2.7Se0.3 composites with excellent thermoelectric and magnetocaloric properties

The core of combining thermoelectric (TE) and magnetocaloric (MC) cooling techniques lies in developing a new material possessing simultaneously large TE and MC cooling performance. In this work, using n-type Bi2Te2.7Se0.3 (BTS) as the TE base material and Gd as the second-phase MC material, Gd/BTS composites were prepared by spark plasma sintering method. In the composites, interfacial reaction between Gd and BTS was identified, resulting in a formation of GdTe, which has a large impact on electron concentration through adjusting defect concentration. The MC/TE composite containing 2.5 wt% Gd exhibited a ZT value of 0.6 at 300 K, essentially retaining the original TE performance, while all the composites largely maintained the excellent MC performance of Gd. This work provides a potential pathway to achieving high performance in MC/TE composites.