Elastic strain constitutes a decisive factor in determining the recoverable deformability of thermoelectric materials. Plastic deformation for microstructure engineering has been demonstrated as a viable approach to enhance the elastic strain. However, this approach is highly dependent on the material’s plasticity, which is rather limited by the rigidity for the majority of inorganic semiconducting thermoelectric materials. Thermocouple materials, as metallic thermoelectric materials, possess a favorable plasticity, motivating this work to focus on the elastic bendability of a metallic thermoelectric generator that is composed of K-type thermocouple components, namely p-type Ni₉₀Cr₁₀ and n-type Ni₉₅Al₂Mn₂Si. The cold-rolling process enables a large elastic modulus and a high yield strength, thanks to the texturized direction along <111>, and dense dislocations and refined grains, respectively, eventually resulting in a 400% increase in the elastic strain. Such superior elasticity ensures the preservation of the initial transport properties for the rolled films even after being bent 100000 times within a radius of ~8 mm. A power output of ~414 μW is achieved in a ten-leg flexible thermoelectric device, suggesting its substantial potential for powering wearable electronics.

Thermal stability of thermoelectric devices plays a pivotal role in their practical applications. Chemical reaction/diffusion between thermoelectric materials and electrodes is one of the primary factors contributing to the degradation/failure of device performance at elevated temperatures. Introducing barrier layers to impede the behavior of chemical reactions has emerged as an effective approach for averting the failure of these devices. In this work, the FeSi is revealed to be a potent material of barrier layer in high-performance Mg₂Si_0.3Sn_0.7 thermoelectric material based on the considerations of interfacial reaction energy and sinterability. The well-established bond in Mg₂Si_0.3Sn_0.7/FeSi joint results in a low contact resistivity of ~20 μΩ⸱cm² and a conversion efficient of ~6.5% for the Mg₂Si_0.3Sn_0.7 single-leg device is achieved at a temperature difference of ~290 K. Long-term measurements of the device at a hot-side temperature of 600 K reveal that the performance remains nearly invariable as time further increases, which suggests that the FeSi layer retards the chemical reaction/diffusion.

Due to the complex crystal structure for low lattice thermal conductivity and the tunable valence bands for superior electronic performance, CaAl₂Si₂-structured AB₂C₂ Zintl compounds have been frequently proven as promising p-type thermoelectric materials. In this work, thermoelectric properties of CaMg₂Bi₂ are systematically investigated in a broad carrier concentration (10¹⁸–10²⁰ cm⁻³) through Ag-doping for comprehensively evaluating its potential for thermoelectric applications. The broad carrier concentration enables a well assessment of the carrier transport properties by single parabolic band with acoustic phonon scattering and a revelation of the carrier transport by multiple valence orbitals when the carrier concentration higher than ~2 × 10¹⁹ cm^–3, leading to a significant enhancement in electronic performance. With the help of additional point defect phonon scattering introduced by BaMg₂Bi₂-alloying, a reduction in lattice thermal conductivity in the entire temperature range and the lowest one of ~0.7 W/m-K are achieved, leading to a 100% enhancement in average zT_ave. in addition to the contribution of a multiband transport. This work not only demonstrates CaMg₂Bi₂ as a promising thermoelectric material, but also provides a well understanding of its underlying material physics.

Convergence of L and Σ valence bands through alloying with monotellurides, has successfully realized the significant zT-enhancement in SnTe thermoelectrics. CdTe, as a solvend introducing Cd-substitution at Sn site, has been demonstrated theoretically and experimentally as an effective agent to reduce the energy difference between two valence bands. However, the low solubility of ~3% for CdTe in SnTe limits the possibility for further zT-enhancement in SnTe, which motivates the existing efforts on increasing solubility of CdTe or exploring Cd-based solvend with higher solubility. Inspired by the solubility as high as 14% for CdSe in SnTe at 1050 K, this work focuses on the effect of CdSe on thermoelectric properties of SnTe. The converged valence bands induced by the heavy Cd-substitution, results in a significant increase in electronic performance. Moreover, CdSe-alloying would simultaneously introduce cation and anion point defects and boundary interfaces of CdSe precipitates, which leads to a strong phonon scattering and therefore a reduced lattice thermal conductivity of ~0.8 W/m-K. As a result, the synergistic effect of electronic and thermal performances results in a peak zT as high as 1.1 at 850 K, demonstrating (SnTe)_1-x(CdSe)_x as the promising thermoelectric materials.