Thermo-electro-magnetic materials with simultaneously large magnetocaloric (MC) and thermoelectric (TE) effects are the core part for designing TE/MC all-solid-state cooling devices. Compositing MC phase with TE material is an effective approach. However, the elemental diffusion and chemical reaction occurring at the two-phase interfaces could significantly impair the cooling performance. Herein, Gd/Bi_0.5Sb_1.5Te₃ (Gd/BST) composites were prepared by a low-temperature high-pressure spark plasma sintering method with an aim to control the extent of interfacial reaction. The reaction of Gd with the diffusive Te and the formation of GdTe nanocrystals were identified at the Gd/BST interfaces by the atomic-resolution microscope. The formed Bi_Te’ antisite defects and enhanced {000 l} preferential orientation in BST are responsible for the increased carrier concentration and mobility, which leads to optimized electrical properties. The heterogeneous interface phases, along with antisite defects, favor the phonon scattering enhancement and lattice thermal conductivity suppression. The optimized composite sintered at 693 K exhibited a maximum ZT of 1.27 at 300 K. Furthermore, the well-controlled interfacial reaction has a slight impact on the magnetic properties of Gd and a high magnetic entropy change is retained in the composites. This work provides a universal approach to fabricating thermo-electro-magnetic materials with excellent MC and TE properties.

Because poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) is water processable, thermally stable, and highly conductive, PEDOT:PSS and its composites have been considered to be one of the most promising flexible thermoelectric materials. However, the PEDOT:PSS film prepared from its commercial aqueous dispersion usually has very low conductivity, thus cannot be directly utilized for TE applications. Here, a simple environmental friendly strategy via femtosecond laser irradiation without any chemical dopants and treatments was demonstrated. Under optimal conditions, the electrical conductivity of the treated film is increased to 803.1 S cm⁻¹ from 1.2 S cm⁻¹ around three order of magnitude higher, and the power factor is improved to 19.0 μW m⁻¹ K⁻², which is enhanced more than 200 times. The mechanism for such remarkable enhancement was attributed to the transition of the PEDOT chains from a coil to a linear or expanded coil conformation, reduction of the interplanar stacking distance, and the removal of insulating PSS with increasing the oxidation level of PEDOT, facilitating the charge transportation. This work presents an effective route for fabricating high-performance flexible conductive polymer films and wearable thermoelectric devices.

Incorporating magnetic nanoparticles in thermoelectric (TE) materials introduce magnetic interfaces with additional electron and phonon scattering mechanism for high TE performance. However, the influence of heterogeneous interfaces between magnetic nanoparticles and TE matrix on electronic and thermal transport remains elusive in the thermo-electric-magnetic nanocomposites. Here, using p-type TE material Bi_0·3Sb_1·7Te₃ (BST) as matrix and magnetocaloric (MC) material La(Fe_0·92Co_0.08)_11.9Si_1.1 (LFS) nanoparticles as a second phase, TE/MC nanocomposites xLFS/BST (x = 0.1%, 0.2%, 0.3% and 0.4%) were synthesized using spark plasma sintering method. The atomic-resolution interfacial structures demonstrate that Te vacancies originating from LFS-BST interfacial reaction decreases the hole concentration of the LFS/BST nanocomposites and enhances the Seebeck coefficient. The LFS/BST nanocomposites exhibit lower thermal conductivity due to enhanced phonon scattering by interfaces and defects. All the nanocomposites have higher ZT than BST matrix, with 0.2%LFS/BST nanocomposite achieving highest ZT = 1.11 at 380 K. At working current 1.4 A, the device fabricated using 0.2%LFS/BST nanocomposite achieves maximal cooling temperature 4.9 K, which is 58% higher than the matrix. Moreover, the MC properties are retained in all the nanocomposites, which make them a promising candidate to achieve high TE performance and dual TE/MC properties for future applications.

The binary skutterudite CoSb₃ is a narrow bandgap semiconductor thermoelectric (TE) material with a relatively flat band structure and excellent electrical performance. However, thermal conductivity is very high because of the covalent bond between Co and Sb, resulting in a very low ZT value. Therefore, researchers have been trying to reduce its thermal conductivity by the different optimization methods. In addition, the synergistic optimization of the electrical and thermal transport parameters is also a key to improve the ZT value of CoSb₃ material because the electrical and thermal transport parameters of TE materials are closely related to each other by the band structure and scattering mechanism. This review summarizes the main research progress in recent years to reduce the thermal conductivity of CoSb₃-based materials at atomic-molecular scale and nano-mesoscopic scale. We also provide a simple summary of achievements made in recent studies on the non-equilibrium preparation technologies of CoSb₃-based materials and synergistic optimization of the electrical and thermal transport parameters. In addition, the research progress of CoSb₃-based TE devices in recent years is also briefly discussed.