Thermoelectric properties of Te-doped ternary CuAgSe compounds

Abstract

Ternary selenide CuAgSe shows a great potential as a new promising thermoelectric material due to the superior carrier mobility and low lattice thermal conductivity. In this study, we doped Te at Se-sites and systematically studied the effect of Te-doping on the thermoelectric properties of low-temperature CuAgSe phase (β-CuAgSe). It is found that the Te doping limit in β-CuAgSe is around 0.15. The longitudinal resistivity and Hall resistivity measurements under magnetic field suggest that Te-doping exerts little effect on the band structure and the low-mobility carriers (holes) contribute weakly to the electrical transports in all Te-doped samples. Thus, the p-n transition and accompanying abrupt Seebeck coefficient decrease at elevated temperature, which are quite common in the non-stoichiometric β-CuAgSe samples, were not observed in Te-doped samples. Although the electrical conductivity of Te-doped samples is reduced due to the decreased carrier concentration and mobility, the significantly decreased thermal conductivity ensures the Te-doped samples still maintaining similar or slightly higher thermoelectric figure of merit (zT) as compared with that of the stoichiometric β-CuAgSe. The maximum zT around 0.7 at 450 K is obtained in CuAgSe0.95Te0.05.

Copper chalcogenide thermoelectric materials

“…By doping Te at Se site, the thermal conductivity was significantly reduced, resulting in a zT=0.7 at 450 K in CuAgSe 0. 95 Te 0.05 [66,95].…”

Enhancement of Power Factor for Inherently Poor Thermal Conductor Ag8GeSe6 by Replacing Ge with Sn

“…The idea is to develop a material which is glassy for phonons and crystalline for charge carriers. In the context of PGEC, various research have been reported with new TE materials with high ZT , such as skutterudites, , clathrates, , and chalcopyrite. , Recently, the superionic compounds such as, Cu 2 X, , Ag 2 X, − CuAgX (where X = S, Se, Te) and CuCrSe 2 have been in the main research focus due to new concept phonon liquid electron crystal (PLEC). These superionic materials have a rigid anion sub lattice to maintain crystalline solid, while the cations have a “liquid-like” movements to scatter the heat carrying acoustic phonons, thus satisfying the PLEC concept.…”

Temperature-Dependent Structural Variation and Cu Substitution in Thermoelectric Silver Selenide

“…Values of κ lat (κ total − κ el ) for all compositions (Figure 5e) lie below 0.5 W m −1 K −1 , which is typical of disordered superionic conductors 32,71 and significantly lower compared to that for most state-of-the-art thermoelectric materials. 17,72−76 The κ lat values of 1 and 5% Cu-containing samples (∼0.3 W m −1 K −1 ) are similar to that for Ag 2 SeS 0.01 , whereas the 10% Cu sample has slightly larger κ lat (∼0.4 W m −1 K −1 ), followed by Ag 2 Se (∼0.5 W m −1 K −1 ) at room temperature.…”

“…The phonon glass–electron crystal (PGEC) concept , is one important strategy for developing high-performing thermoelectric materials, where the phonon glass region provides the disorder necessary to scatter phonons (i.e., low κ total ) without significantly affecting the carrier mobility in the electron crystal region (i.e., high S 2 /ρ). The most notable systems which follow the PGEC behavior are nanostructured materials consisting of nanoparticles embedded in the host matrix that effectively scatter phonons without interfering with the carrier transport, − such as in PbTe alkaline earth element; − rattling-like behavior of guest atoms in certain host electron–crystal structures with voids, such as clathrates , and filled skutterudites; , layered systems, such as layered cobaltite oxides , and layered sulfides; − and liquid-like behavior of superionic conductors, where the metal ions are mobile within a rigid Se lattice, such as Cu 2 Se, , CuAgSe/Te, − and Ag 2 Se. , …”