Copper ion liquid-like thermoelectrics

Abstract

Advanced thermoelectric technology offers a potential for converting waste industrial heat into useful electricity, and an emission-free method for solid state cooling. Worldwide efforts to find materials with thermoelectric figure of merit, zT values significantly above unity, are frequently focused on crystalline semiconductors with low thermal conductivity. Here we report on Cu(2-x)Se, which reaches a zT of 1.5 at 1,000 K, among the highest values for any bulk materials. Whereas the Se atoms in Cu(2-x)Se form a rigid face-centred cubic lattice, providing a crystalline pathway for semiconducting electrons (or more precisely holes), the copper ions are highly disordered around the Se sublattice and are superionic with liquid-like mobility. This extraordinary 'liquid-like' behaviour of copper ions around a crystalline sublattice of Se in Cu(2-x)Se results in an intrinsically very low lattice thermal conductivity which enables high zT in this otherwise simple semiconductor. This unusual combination of properties leads to an ideal thermoelectric material. The results indicate a new strategy and direction for high-efficiency thermoelectric materials by exploring systems where there exists a crystalline sublattice for electronic conduction surrounded by liquid-like ions.

Heavy Doping by Bromine to Improve the Thermoelectric Properties of n‐type Polycrystalline SnSe

“…)3, 4, 5 and decreased thermal conductivity by defect engineering,6 and nanoengineering 7, 8, 9. An alternative way to achieve high ZT values is to seek new classes of TE materials with intrinsically low thermal conductivity, such as clathrates, skutterudites, sulfur‐based compounds, Ag 9 GaSe 6 , and SnSe etc 10, 11, 12, 13, 14…”

Ultrahigh Power Factor in Thermoelectric System Nb0.95M0.05FeSb (M = Hf, Zr, and Ti)

“…One effective strategy for ZT improvement is to minimize the lattice thermal conductivity by scattering phonons off crystal defects, e.g., grain boundaries,9, 10, 11, 12, 13, 14 dislocations,15, 16, 17, 18 point defects,19, 20, 21, 22, 23, 24, 25 nanoprecipitates,26, 27, 28, 29, 30 etc. However, thermoelectric power generation demands not only high ZT but also high PF over a wide range of temperature, which directly determines output power density ω, another crucial parameter for power generation 31, 32, 33.…”

“…Such a substantial enhancement is mainly ascribed to the improved carrier mobility (>20 cm 2 V −1 s −1 at 300 K). As a result, this p‐type NbFeSb system possesses more competitive PF than other high‐performance thermoelectric materials (e.g., lead telluride, bismuth telluride, etc 10, 12, 29, 35, 56, 57, 58, 59 1 .…”

“…Comparison of temperature‐dependent PF among Nb 0.95 M 0.05 FeSb (M = Hf, Zr, Ti) and other high‐performance thermoelectric materials 10, 12, 29, 33, 35, 56, 57, 58, 59…”

Enhancing the Figure of Merit of Heavy‐Band Thermoelectric Materials Through Hierarchical Phonon Scattering

“…Current efforts to improve zT are focused on the optimization of power factor α 2 σ through controlled doping or electron band engineering,7, 8, 9, 10, 11 suppression in κ L by alloying or nanostructuring,1, 2, 5, 6 and development of new materials with intrinsically low κ L 12, 13, 14, 15. Heat‐carrying phonons cover a broad spectrum of frequency, and the κ L is a sum of contributions from phonons of different frequencies.…”