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Grain boundary plays a vital role in thermoelectric transports, leading to distinct properties between single crystals and polycrystals. Manipulating the grain boundary to realize good thermoelectric properties in polycrystals similar as those of single crystals is a long-standing task, but it is quite challenging. Herein, we develop a liquid-phase sintering strategy to successfully introduce Mg2Cu nano-sintering-aid into the grain boundaries of Mg3(Bi, Sb)2-based materials. The nano-aid helps to enlarge the average grain size to 23.7 μm and effectively scatter phonons, leading to excellent electrical transports similar as those of single crystals and ultralow lattice thermal conductivity as well as exceptional thermoelectric figure of merit (1.5 at 500 K) and conversion efficiency (7.4% under temperature difference of 207 K). This work provides a simple but effective strategy for the fabrication of high-performance polycrystals for large-scale applications. The authors develop a liquid-phase sintering strategy to effectively enlarge material's grain sizes, thereby achieving single crystal-like electronic transport properties in polycrystalline Mg3(Bi, Sb)2. [ABSTRACT FROM AUTHOR]

Deformable thermoelectrics have great potential in self‐powered flexible or hetero‐shaped electronics. The exceptional room‐temperature plasticity recently discovered in several inorganic semiconductors makes it possible to develop new thermoelectric (TE) materials with both high performance and intrinsic deformability. Nonetheless, all the known plastic or ductile TE materials are n‐type semiconductors. It is urgent to explore p‐type counterparts for device design and fabrication. In this study, the first p‐type plastic inorganic TE material is reported. Via alloying Cu in n‐type plastic Ag2S0.7Se0.3 to modulate the charged crystal defects, (Ag1−xCux)2S0.7Se0.3 (x = 0.7–0.8) can simultaneously realize good plasticity and p‐type conduction. Particularly, (Ag0.2Cu0.8)2S0.7Se0.3 with a hexagonal structure shows a maximum zT of 0.42 at 800 K. Via the introduction of Cu deficiencies, the good plasticity is well maintained while the maximum zT is greatly enhanced to 0.95 at 800 K, a record‐high value for plastic TE materials. This study is expected to accelerate the development of plastic TE semiconductors and full‐inorganic deformable TE devices for the application in hetero‐shaped power generators. [ABSTRACT FROM AUTHOR]

Element doping/alloying is a common strategy to tune the electrical and thermal transports of thermoelectric (TE) materials, but the doping/alloying limit of foreign elements in many TE materials is usually very low, bringing a great challenge to improve the TE performance. In this work, beyond the classic principle of “like dissolves like,” it is found that choosing the compound with a severely distorted lattice and diversified chemical bonding as the matrix also facilitates achieving a high doping/alloying limit. Taking ductile semiconductors as an example, this work shows that gold (Au) element is nearly immiscible in Ag2S and Ag2Te, but has a relatively high alloying limit in complex Ag2S0.5Te0.5 meta‐phase. Au in Ag2S0.5Te0.5 significantly decreases the carrier concentration and improves the TE performance, but scarcely changes the mechanical properties. Consequently, Ag1.99Au0.01S0.5Te0.5 demonstrates both a high figure‐or‐merit of 0.95 at 550 K and extraordinary room‐temperature ductility. This work offers an effective and general strategy to develop stabilized doped/alloyed TE materials. [ABSTRACT FROM AUTHOR]

Keywords: defect engineering; flexible electronics; plastic inorganic semiconductors; thermoelectrics EN defect engineering flexible electronics plastic inorganic semiconductors thermoelectrics 1 1 1 06/21/21 20210617 NES 210617 In article number 2100883, Pengfei Qiu, Tian-Ran Wei, Xun Shi, and co-workers develop the first p-type plastic inorganic thermoelectric material. Thermoelectrics: p-Type Plastic Inorganic Thermoelectric Materials (Adv. Defect engineering, flexible electronics, plastic inorganic semiconductors, thermoelectrics. [Extracted from the article]

α-MgAgSb is considered as a potential near-room-temperature thermoelectric material in virtue of its excellent electrical properties, ultralow lattice thermal conductivity and abundant constituent elements. However, it is hard to obtain high-quality phase pure α-MgAgSb due to its complex phase transition and high reactivity of element Mg, which cloaks material's intrinsic thermoelectric performance. Herein, through adopting a tantalum-sealing melting technique, we achieved highly-quality pure α-MgAgSb with large grain size and less oxygen content, as compared with our ball milled samples. The as-synthesized tantalum-sealing melted α-MgAgSb, without element doping or alloying, exhibited intrinsically low thermal conductivity, large weighted mobility, and high carrier concentration closes to the optimum range. Eventually, we attained a maximum thermoelectric figure of merit zT value of 1.3 at around 500 K in the tantalum-sealing melted α-MgAgSb. The average power factors and average zT values are also as high as 25 μW cm−1 K−2 and 1.1 respectively in the low-temperature range of (300 - 550) K, both of which rank as top values among the known materials. This study not only sheds new light on the understanding of intrinsic properties of α-MgAgSb but also demonstrates its great promise for harvesting low-grade waste heat. Record-high average power factor of 25 μW cm−1 K−2 and average zT of 1.1 were achieved in the melted α-MgAgSb sythesized by the tantalum-sealing melting technique. [Display omitted] [ABSTRACT FROM AUTHOR]