Alloying Cr2/3Te in AgCrSe2 compound for improving thermoelectrics

Abstract

AgCrSe2, which crystallizes in alternative layers of Ag+ and CrSe2− octahedral structure, has shown great potential as good thermoelectric material due to its unique ultralow lattice thermal conductivity. In this work, compound Cr2/3Te is alloyed with the matrix Ag0.97CrSe2 and the carrier concentration ranges within 1018–1020 cm−3, enabling a reliable assessment of transport properties based on single parabolic band model at room temperature. Moreover, homogeneous nanoprecipitate is observed in the matrix for high Cr2/3Te content samples, which leads to the scattering of main heat carrier of long-wavelength phonons, and thus a slight reduction of lattice thermal conductivity (∼0.3 W/m K) compared with intrinsic AgCrSe2. Combined with the optimized carrier concentration and the low lattice thermal conductivity, a figure of merit zT of 0.6 at 650 K is achieved, exceeding other reported AgCrSe2 systems, demonstrating the current Ag0.97CrSe2(Cr2/3Te)x materials as good potential thermoelectrics.

Advancing thermoelectrics by suppressing deep-level defects in Pb-doped AgCrSe2 alloys

“…which is higher than the majority of previous reports (see Fig. S5), [29,36,37,40] illustrating that the Pb doping can effectively enhance the electrical properties.…”

“…Additionally, both the solid solution of similarly structured compounds and secondary phase precipitates in AgCrSe 2 show enhanced phonon scattering effects, further reducing the κ L . [28,40] In this work, we have investigated the influence of Pb doping on the thermoelectric properties of Ag 0.97 CrSe 2 with Ag vacancies on the basis of the above requirements. The Pb 2+ is introduced as an acceptor dopant into the Cr sites, which increases p H from 3×10 18 cm −3 to 1.77×10 19 cm −3 at room temperature.…”