PbTe-based alloys have been widely used as mid-temperature thermoelectric (TE) materials since the 1960s. Years of endeavor spurred the tremendous advances in their TE performance. The breakthroughs for n-type PbTe have been somewhat less impressive, which limits the overall conversion efficiency of a PbTe-based TE device. In light of this obstacle, an n-type Ga-doped PbTe via an alternative thermodynamic route that relies on the equilibrium phase diagram and microstructural evolution is revisited. Herein, a plateau of zT = 1.2 is achieved in the best-performing Ga 0.02 Pb 0.98 Te in the temperature range of 550-673 K. Notably, an extremely high average zT ave = 1.01 is obtained within 300 − 673 K. The addition of gallium optimizes the carrier concentration and boosts the power factor PF = S 2 ρ −1. Meanwhile, the κ L of Ga-PbTe reveals a significantly decreasing tendency owing to the defect evolution that changes from dislocation loop to nano-precipitation with increasing Ga content. The pathway for both the κ L reduction and defect evolution can be probed by an equilibrium phase diagram, which opens up a new avenue for locating high zT TE materials.

Zn 4 Sb 3 -based compounds constitute a lead-free material family with a best thermoelectric figure of merit (zT) in the midtemperature range. Unlike being a stoichiometric compound, the mutual solubility of Zn and Sb elicits rich microstructures and the structural instability of Zn 4 Sb 3 . The solubility limit and neighboring phase relations are crucial for the delicate balance between the thermoelectric performance and phase stability of Zn 4 Sb 3 . In this work, we constructed the isothermal section of the Zn−Sb−In ternary phase diagram, built the zT map near the β-Zn 4 Sb 3 phase region, and showed that the formation of multiscale microstructures has a profound impact on the electronic and phonon transport properties and phase stability. A high-zT zone was identified near the phase boundary between the twophase InSb + Zn 5 Sb 4 In 2 and the three-phase Zn 4 Sb 3 + InSb + Zn 5 Sb 4 In 2 regions. A sample with a nominal composition of Zn 3.8 In 0.2 Sb 3 exhibited an ultralow κ L of 0.2 (W m −1 K −1 ), an enhanced PF of 1.75 (mW m −1 K −2 ), and a remarkable zT value of 1.8 at 698 K. These state-of-the-art thermoelectric properties were attributed to the simultaneous enhancement in phonon scattering and the carrier energy-filtering effect in a unique hierarchical microstructure, in which InSb nanoprecipitates are dispersed in Zn 5 Sb 4 In 2 coarse grains, and the latter are embedded in the host matrix In−Zn 4 Sb 3 . These results opened an avenue for environmentally friendly cost-effective midtemperature thermoelectric materials.

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Aluminum alloys, which serve as heat sink in light-emitting diode (LED) lighting, are often inherent with a high thermal conductivity, but poor thermal total emissivity. Thus, high emissive coatings on the Al substrate can enhance the thermal dissipation efficiency of radiation. In this study, the ultrasonic mechanical coating and armoring (UMCA) technique was used to insert various ceramic combinations, such as Al2O3, SiO2, or graphite, to enhance thermal dissipation. Analytic models have been established to couple the thermal radiation and convection on the sample surface through heat flow equations. A promising match has been reached between the theoretical predictions and experimental measurements. With the adequate insertion of ceramic powders, the temperature of the Al heat sinks can be lowered by 5–11 °C, which is highly favorable for applications requiring cooling components.

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