It is known that the electronic transport and heat conduction of thermoelectric materials are very sensitive to structural changes. In this article, the effect of Ag substitution on the crystal structure and hence thermoelectric properties of Cu 1−x Ag x InTe 2 (x = 0, 0.05, 0.15, 0.25, 0.50, 0.75, and 1.00) solid solutions are investigated. The structural analysis shows that with the increasing Ag content, the lattice strain changes from tensile stress to compressive stress, and the tetrahedral distortion first relieves and then aggravates, which influences not only electronic but also thermal transport properties. The replacement of Cu by Ag results in the reduction of carrier concentration and lattice thermal conductivity. Although the enhancement in zT values of Cu 1−x Ag x InTe 2 samples mainly originates from the significantly reduced lattice thermal conductivity, the improved electronic transport properties due to Ag substitution also play an important role. As a result, a maximum zT value of ∼1.36 is achieved for Cu 0.75 Ag 0.25 InTe 2 at 823 K, which is a 92% improvement compared with the value of pristine CuInTe 2 . Our study provides a primary view of the relationship between the structure and thermoelectric performance, which is beneficial to the optimization of thermoelectric properties.

Recent advances in high-throughput (HTP) computational power and machine learning have led to great achievements in exploration of new thermoelectric materials. However, experimental discovery and optimization of thermoelectric materials have long relied on the traditional Edisonian trial and error approach. Herein, we demonstrate that ultrahigh thermoelectric performance in a Cu-doped PbSe-PbS system can be realized by HTP experimental screening and precise property modulation. Combining the HTP experimental technique with transport model analysis, an optimal Se/S ratio showing high thermoelectric performance has been efficiently screened out. Subsequently, based on the screened Se/S ratio, the doping content of Cu has been subtly adjusted to reach the optimum carrier concentration. As a result, an outstanding peak zT~1.6 is achieved at 873 K for a 1.8 at% Cu-doped PbSe0.6S0.4 sample, which is the superior value among the n-type Te-free lead chalcogenides. We anticipate that current work will stimulate large-scale unitization of the HTP experimental technique in the thermoelectric field, which can greatly accelerate the research and development of new high-performance thermoelectric materials.

Bi 2 Te 3 -based compounds are exclusive commercial thermoelectric materials around room temperature. For n-type compounds, optimal thermoelectric properties are normally obtained at temperatures higher than room temperature to suppress the bipolar effect through increased carrier concentration. We find that doping with trace amounts of Cd and the addition of excess Bi are effective ways to optimize carrier concentration and achieve enhanced room-temperature thermoelectric performance for the Bi 2 Te 2.7 Se 0.3 alloy in this work. For the Cd-doped samples, the replacement of Cd with Bi leads to not only a significant decrease in electron concentration but also apparently reduces the total thermal conductivity. The addition of excess Bi in the samples creates a Bi-rich synthetic atmosphere during the synthesis process, leading to increased Bi Te antisite defects, decreased electron concentration, and reduced total thermal conductivity. Doping a small amount of Cd or adding excess Bi causes optimal thermoelectric performance of the n-type Bi 2 Te 2.7 Se 0.3 sample shifts obviously toward low temperatures, and the samples with 0.4 atom % Cd and 0.8 atom % excess Bi achieve maximum zT of ∼0.97 at 448 K and ∼0.88 at 348 K, respectively.

Half-Heusler materials are promising candidates for high-temperature power generation and have relatively high lattice thermal conductivity compared to other thermoelectric material systems. In this work, we report novel p-type YbNiSbbased half-Heusler alloys with a low lattice thermal conductivity (∼3.6 W m −1 K −1 at 340 K) that resulted from their large Gruneisen parameter, low sound speed, and low Debye temperature. All YbNiSb-based alloys exhibit a high carrier mobility of 30−50 cm 2 V −1 s −1 at room temperature because of their relatively small effective mass. Importantly, the structural analysis reveals that Yb-rich Yb 1.3 Ni 0.9 Sb 0.8 exhibits Yb/Ni and Yb/Sb substitution, indicating a wide homogeneity region of the YbNiSb phase experimentally. The adjustable Yb and Ni contents in YbNiSb-based alloys can modify the band structure around the Fermi level and significantly affect electrical transport properties. Additionally, by doping Ta at Yb sites, the carrier concentration and lattice thermal conductivity of these alloys can be manipulated. Consequently, a peak zT value of 0.45 at 823 K was achieved for Yb 0.95 Ta 0.05 NiSb. Our work demonstrates that YbNiSb-based alloys are promising p-type thermoelectric materials and suggests the possibility of exploring novel thermoelectric alloys in rare-earth nickel pnictides via tuning their composition and crystal structure.