The widespread use of thermoelectric technology is constrained by a relatively low conversion efficiency of the bulk alloys, which is evaluated in terms of a dimensionless figure of merit (zT). ThezTof bulk alloys can be improved by reducing lattice thermal conductivity through grain boundary and point-defect scattering, which target low- and high-frequency phonons. Dense dislocation arrays formed at low-energy grain boundaries by liquid-phase compaction in Bi0.5Sb1.5Te3(bismuth antimony telluride) effectively scatter midfrequency phonons, leading to a substantially lower lattice thermal conductivity. Full-spectrum phonon scattering with minimal charge-carrier scattering dramatically improved thezTto 1.86 ± 0.15 at 320 kelvin (K). Further, a thermoelectric cooler confirmed the performance with a maximum temperature difference of 81 K, which is much higher than current commercial Peltier cooling devices.

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Pavonite homologues, Cu x+y Bi 5Ày Se 8 (1.2 # x # 1.5, 0.1 # y # 0.4), in a polycrystalline bulk form have been synthesized using a conventional solid state sintering technique. Their thermal and electronic transport properties were evaluated for mid-temperature thermoelectric power generation applications. Structural complexity, based on unique substitutional and interstitial Cu atoms in the structure, makes this system attractive as an intrinsic low thermal conductivity material; also the band structure calculations revealed that interstitial Cu atoms generate n-type carrier conduction. Room temperature lattice thermal conductivities ranging between 0.41 W m À1 K À1 and 0.55 W m À1 K À1 were found for Cu x+y Bi 5Ày Se 8 ; these values are comparable to those of the state-of-the-art low lattice thermal conductivity systems. These extremely low thermal conductivities combined with the power factors result in the highest ZT ¼ 0.27 at 560 K for Cu 1.9 Bi 4.6 Se 8 .

The hybrid structure of Ag nanowires (AgNWs) covered with graphene (Gr) shows synergetic effects on the performance of transparent conducting electrodes (TCEs). However, these effects have been mainly observed via large-scale characterization, and precise analysis at the nanoscale level remains inadequate. Here, we present the nanoscale verification and visualization of the improved chemical and electrical stabilities of Gr-covered AgNW networks using conductive atomic force microscopy (C-AFM), Auger electron spectroscopy (AES), and X-ray photoelectron spectroscopy (XPS) combined with the gas cluster ion beam (GCIB) sputtering technique. Specifically by transferring island Gr on top of the AgNW network, we were able to create samples in which both covered and uncovered AgNWs are simultaneously accessible to various surface-characterization techniques. Furthermore, our ab initio molecular dynamics (AIMD) simulation elucidated the specific mechanistic pathway and a strong propensity for AgNW sulfidation, even in the presence of ambient oxidant gases.