Half-Heusler (HH) compounds are important high temperature thermoelectric (TE) materials and have gained ever-increasing popularity. In recent years, p-type FeNbSb-based heavy-band HH compounds have attracted considerable attention with the record-high zT value of 1.5. Here, we use first-principles based methods to predict a very high zT value of 1.54 at 1200 K in p-type RuTaSb alloys. The high band degeneracy and low band effective mass contribute to a high power factor. Although the electrical thermal conductivity is high due to the high carrier mobility and hence electrical conductivity, the total thermal conductivity is moderate because of the low lattice thermal conductivity. The predicted high zT demonstrates that the p-type RuTaSb HH alloys are promising as TE materials for high temperature power generation.

Single-crystal trigonal tellurium nanowires and nanotubes were synthesized using a facile, efficient, and relatively green solution phase method with ethylene glycol as solvent and an alternative reducing agent in the presence of NaOH. Large-scale production of slender nanowires and hollow nanotubes with average diameters of 72 and 240 nm, respectively, was achieved by increasing the temperature from 170 °C to 200 °C. Tellurium morphology from nanowires to nanotubes was also controlled by adjusting the NaOH dosage. Scanning electron micrographs show that low temperature or NaOH insufficiency promotes the formation of slender nanowires but counteracts the synthesis of tellurium nanotubes. Detailed reaction equations based on the NaOH dosage were obtained. Preferential growth orientation of [001] was observed in the nanowire and nanotube through high-resolution transmission electron microscopy. Further formation mechanisms dependent on time were systematically studied.

By optimizing the concentration of the substitutional defect Pr_Mg1, Mg_3.2Pr_0.02Sb_1.5Bi_0.5 exhibits a peak zT value of 1.70 at 725 K.

The maximum ZT of n-type Mg₃Sb₂ can be up to 3.1.