High Thermoelectric Performance in the New Cubic Semiconductor AgSnSbSe₃ by High-Entropy Engineering

Abstract

We investigate the structural and physical properties of the AgSnmSbSem+2 system with m=1-20 (i.e. SnSe matrix and ~5-50 % AgSbSe2) from length scales ranging from atomic, nano and macro. We find the 50:50 composition, with m=1 (i.e. AgSnSbSe3), forms a stable cation disordered cubic rock-salt p-type semiconductor with a special multipeak electronic valence band structure. AgSnSbSe3 has an intrinsically low lattice thermal conductivity of ~0.47 Wm -1 K -1 at 673 K owing to the synergy of cation disorder, phonon anharmonicity, low phonon velocity, and low-frequency optical modes. Furthermore, Te alloying on the Se sites creates a quinary high entropy NaCl-type solid solution AgSnSbSe3-xTex with randomly disordered cations and anions. The extra point defects and lattice dislocations lead to glass-like lattice thermal conductivities of ~0.32 Wm -1 K -1 at 723 K and higher hole carrier concentration than AgSnSbSe3. Concurrently, the Te alloying promotes greater convergence of the multiple valence band maxima in AgSnSbSe1.5Te1.5, the composition with the highest configurational entropy. Facilitated by these favorable modifications, we achieve a high average power factor of ~9.54 μWcm -1 K -2 (400-773 K), a peak thermoelectric figure of merit ZT of 1.14 at 723 K and a high average ZT of ~1.0 over a wide temperature range of 400-773 K in AgSnSbSe1.5Te1.5.

n-Type thermoelectric metal chalcogenide (Ag,Pb,Bi)(S,Se,Te) designed by multi-site-type high-entropy alloying

“…Finally, S mix (total) = 2.00R can be obtained. Let us mention that a similar situation has already been seen for CsCl-type superconductors (Sc,Zr,Nb,Ta) 0.65 (Rh,Pd) 0.35 reported by Stolze et al [36] and NaCl-type MCh [22,28,29]. The obtained S mix exhibited the highest S mix (total) value among all HEA thermoelectric materials.…”

“…However, the ZT values are low due to the high σ , low S and high κ. After the report, some papers incorporating the HEA concept into thermoelectric materials have been reported: such as half-Huesler; NdFeSb-based [26], Ti 2 NiCoSnSb [27] and MCh; AgSnSbSe 3−x Te x [28]. Among them, AgSnSbSe 3−x Te x exhibited high ZT values of 1.14 at 723 K as p-type thermoelectric materials.…”

High-entropy ceramics: Present status, challenges, and a look forward

“…Luo et al [251] synthesized high-entropy SnSe-based materials to search for higher zT values. AgSbSe 2 was adopted to introduce cation disorder for restricting κ and inducing special multi-peak electronic valence band.…”

High Entropy Semiconductor AgMnGeSbTe4 with Desirable Thermoelectric Performance

“…[18] In recent years, high entropy materials have attracted increasing attention from the thermoelectric community due to its high crystal symmetry and serious lattice distortion. [4,19,20] First, enhanced configuration entropy can improve the solubility of atoms and the stability of crystal structure (e.g., PbSe). [4] Second, high crystal symmetry is expected to enhance the electrical transport properties for thermoelectric materials (e.g., GeTe).…”