Anomalous transport and thermoelectric performances of CuAgSe compounds

Abstract

The copper silver selenide has two phases: the low-temperature semimetal phase (α-CuAgSe) and high-temperature phonon-glass superionic phase (β-CuAgSe). In this work, the electric transport and thermoelectric properties of the two phases are investigated. It is revealed that the β-CuAgSe is a p-type semiconductor and exhibits low thermal conductivity while the α-CuAgSe shows metallic conduction with dominant n-type carriers and low electrical resistivity. The thermoelectric figure of merit zT of the polycrystalline β-CuAgSe at 623 K is ~0.95, suggesting that superionic CuAgSe can be a promising thermoelectric candidate in the intermediate temperature range.

Ambient Scalable Synthesis of Surfactant-Free Thermoelectric CuAgSe Nanoparticles with Reversible Metallic-n-p Conductivity Transition

“…19 Our ZT values above 575 K are comparable to the bulk value (0.9 vs. 0.95 at 623 K) due to the extremely low thermal conductivity. The valley-like ZT profiles suggest the minimum value near the phase transition temperature (467 K), and it drastically increased from 0.1 at 470 K to 0.8 at 500 K. This anomalous behavior is consistent with previous reports on thermoelectric materials with phase transition.…”

“…The results show that electrons are the main charge carriers in CuAgSe below 300 K. The carrier density (n) is approximately 10 18 and decreases with rising temperature, while the carrier mobility first decreases from 7478 to 1798 cm 2 /(V·s) with increasing temperature from 3 K to 200 K, then slightly increases to 1966 cm 2 /(V·s) at 300 K. The carrier density is almost the same but the carrier mobility is significantly reduced by nanostructure compared with bulk CuAgSe. [18][19] The thermoelectric properties of sintered CuAgSe nanoparticles above room temperature were further investigated, and Figure 7 displays the results measured from room temperature to 623 K. The differences between the results around room temperature shown in Figures 4 and 7 originated from the error of different instruments. A reversible first order phase transition is proved by the heating-cooling DSC curve displayed in Figure S4(a).…”

“…Increase of temperature leads to the transition from mixed orthorhombic and tetragonal phases into cubic structure, which has been reported in the bulk CuAgSe. 19 The overall and lattice thermal conductivities (κ lattice = κ-…”

“…Extremely high electron mobility at low temperature and a ZT of 0.15 at room temperature and a ZT of 0.95 at 623 K have been reported in bulk CuAgSe. [18][19] It should be noted that most research has been focused on bulk CuAgSe prepared by the solid state reaction at high temperature (> 1000 K), [18][19] and there is no report on the thermoelectric properties of CuAgSe sintered from its nanostructures due to the difficulties in efficient preparation of CuAgSe nanomaterials on a large scale. Small-scale CuAgSe nanotubes and dendrites can be prepared from Se and Ag 2 Se nanotemplates, respectively.…”

Extremely low thermal conductivity and high thermoelectric performance in liquid-like Cu2Se1−xSx polymorphic materials

“…[11][12][13][14][15] The rigid anion sublattice provides a crystalline pathway for electrons transport, while the liquid-like cation sublattice can greatly scatter the heat-carrying phonons and even eliminate some of the transverse vibrational modes, leading to simultaneously shortened phonon mean free path and reduced heat capacity below the Dulong-Petit value at high temperatures. 11,13 Motivated by the PLEC concept, many superionic compounds, such as Cu2-xδ (δ = S, Se, Te), 11,12,[16][17][18][19][20] CuAgSe, 21,22 Cu5FeS4, 23 Ag/Cu-based chromium diselenides, 14,24 and argyrodite-type compounds, 15 have been discovered with ultra-low thermal conductivity and high zT values. Among them, copper chalcogenides Cu2-xδ (δ= S, Se, Te) have attracted great attentions due to their unique features of environmentally benign, low-cost, and earth-abundant.…”