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Despite the fact that research into most high-performance thermoelectric (TE) materials is focused on tellurides, compelling demand has arisen to replace tellurium (Te) with selenium (Se) due to the scarcity of Te. Silver bismuth diselenide (AgBiSe2, ABS) has been widely studied in relation to thermoelectric applications due to its intrinsically low thermal conductivity. However, its low power factor (PF) has been considered as an underlying issue preventing improvements of the TE properties of ABS. Here, it is demonstrated that a high PF can be achieved by incorporating Cu into the ABS system via the nestification of conduction bands when a disordering between Ag and Bi occurs. Degenerate electronic bands simultaneously increase the density-of-states effective mass and carrier concentration while not reducing the carrier mobility significantly. Therefore, improved TE performance with a maximum PF of 8.2 μW cm−1 K−2 and a peak zT value of 1.14 was achieved at 773 K, opening a new horizon for the development of environmentally benign TE materials with high performance capabilities. [ABSTRACT FROM AUTHOR]

The selective reduction of thermal conductivity while preserving the Seebeck coefficient and electrical conductivity is regarded as a key strategy for achieving the high dimensionless figure-of-merit (ZT) of thermoelectric materials. Here, we newly propose a periodic three-dimensional (3D) nanostructure that has an ability to significantly reduce thermal conductivity, resulting in an improved ZT value of thermoelectric materials near room temperature. A 3D nanostructured thermoelectric monolith is developed by electrochemical deposition of a Bi–Sb–Te ternary alloy into a highly ordered, interstitial porous network in an epoxy template predefined by advanced lithography. The resultant inch-scale, bicontinuous nanocomposite monolith released from a substrate can be easily transferred to a customized reliable platform for evaluating thermoelectric properties. The measured thermal conductivity is only ∼0.89 W mK−1 at 350 K due to greatly increased phonon boundary scattering without any degradation in the Seebeck coefficient and electrical conductivity, leading to an enhanced ZT value (∼0.56) which is ∼50% higher than that of an ordinary film with the same elemental composition. The 3D nanostructure developed here will provide new design opportunities for nanostructured thermoelectric materials, potentially usable in flexible thermoelectric coolers and wearable energy harvesting systems. [ABSTRACT FROM AUTHOR]

Silver chalcogenides have received much attention in potential thermoelectric materials research because of high carrier mobility and low effective mass. Among them, in Ag2Te, it was reported that the phase transition from monoclinic to cubic phase occurs at relatively low temperatures, so that extensive research for effective application using this material has been aroused. In this work, we investigated how 1-dimensional nanostructure affects the thermoelectric properties through as-synthesized single crystalline Ag2Te nanowires. Adopting well-defined thermoelectric MEMS device structure and transferring an individual Ag2Te nanowire, we measure electrical resistance and Seebeck coefficient as a function of temperature. When the phase changes from monoclinic to cubic, the resistance increases, while absolute Seebeck coefficient value decreases. These results are compared with previous reports for Ag2Te bulk and film, suggesting the increased density of states of the carriers due to nanowire structure. [ABSTRACT FROM AUTHOR]

Charge carrier transport and corresponding thermoelectric properties are often affected by several parameters, necessitating a thorough comparative study for a profound understanding of the detailed conduction mechanism. Here, as a model system, we compare the electronic transport properties of two layered semiconductors, Sb 2 Si 2 Te 6 and Bi 2 Si 2 Te 6 . Both materials have similar grain sizes and morphologies, yet their conduction characteristics are significantly different. We found that phase boundary scattering can be one of the main factors for Bi 2 Si 2 Te 6 to experience significant charge carrier scattering, whereas Sb 2 Si 2 Te 6 is relatively unaffected by the phenomenon. Furthermore, extensive point defect scattering in Sb 2 Si 2 Te 6 significantly reduces its lattice thermal conductivity and results in high zT values across a broad temperature range. These findings provide novel insights into electron transport within these materials and should lead to strategies for further improving their thermoelectric performance.