Cu2Se based thermoelectric materials are of great potential for high‐temperature energy harvesting due to their high‐temperature figure‐of‐merit (zT). For further development of Cu2Se, both engineering and mid‐temperature figure‐of‐merit need to be improved. In this work, we report that carbon‐coated boron (C/B) nanoparticles incorporation can significantly improve both mid‐ and high‐temperature zT in Cu2Se. The nanoparticle inclusions can result in a homogeneous distribution of Cu:C:B interfaces responsible for both improvement of the Seebeck coefficient and significantly reduction in thermal conductivity. Ultrahigh mid‐ and high temperature thermoelectric performance with zT = 1.7 at 700 K and 2.23 at 1000 K as well as significantly improved engineering zT are achieved in the C/B incorporated Cu2Se with desirable mechanical properties and cycling stability. Our findings will stimulate further study and exploration for the Cu2Se based thermoelectric materials for broad applications in converting waste heat to electricity with competitive energy conversion efficiency.

By applying the melt-centrifugation, porosity and dislocations are introduced in the microstructure of the n-type Zintl phase Mg3+xSb1.5Bi0.49Te0.01leading to significantly low κl (∼ 0.33 W m−1 K−1 at 723 K) and enhanced zT (∼ 1.64 at 723 K).

The binary copper chalcogenides Cu 2−δ X (X = S, Se, and Te) have recently gained significant interest due to their high thermoelectric performance at moderate temperatures. In an effort to unveil new Cu-based compounds with promising thermoelectric potential, Cu 3−x Te 2 rickardite mineral emerged as a candidate based on a purely text mining approach applied by a machine learning method. Polycrystalline samples of Cu 3−x Te 2 within the homogeneity range (x = 0.1, 0.2) were successfully synthesized from the raw elements by a solid-state method. High-temperature powder Xray diffraction combined with differential scanning calorimetry and specific heat measurements showed several reversible phase transitions at around 458, 640, and 647 K. Signatures of these transitions were observed on the electronic and thermal transport properties, measured over a broad range of temperatures (5−733 K). The transition undergone by this compound at 647 K results in a crossover from metallic-like to semiconducting-like properties. The combination of high power factor and low thermal conductivity in the high-temperature phase results in improved thermoelectric performances with a peak dimensionless thermoelectric figure-of-merit zT of ∼0.14 at 733 K. The synthetic rickardite mineral is an exciting candidate to be used as a phase change material in broad application areas such as in waste heat harvesting and photovoltaic systems.