High-Temperature Structural and Thermoelectric Study of Argyrodite Ag 8 GeSe 6

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Argyrodites with a general chemical formula of A 8 BC 6 are known for complex phase transitions, ultralow lattice thermal conductivity, and mixed electronic and ionic conduction. The coexistence of ionic conduction and promising thermoelectric performance have recently been reported in selenide and telluride argyrodites, but scarcely in sulfide argyrodites. Here, the thermoelectric properties of Ag 8 Sn(S 1−x Se x ) 6 are reported. Specifically, Ag 8 SnS 6 exhibits intrinsically ultralow lattice thermal conductivities of 0.61-0.31 W m −1 K −1 over the whole temperature range from 32 to 773 K due to distorted local crystal structure, relatively weak chemical bonding, rattler-like Ag atoms, low-lying optical modes, and dynamic disorder of Ag ions at high temperatures. Se doping shifts the orthorhombic-cubic phase transition from 457 K at x = 0 to 430 K at x = 0.10, thereby expanding the temperature range of the thermoelectrically favored cubic phase. A figure of merit zT value ≈ 0.80 is achieved at 773 K in Ag 8 Sn(S 1−x Se x ) 6 (x = 0.03), the highest zT value reported in sulfide argyrodites. These results fill a knowledge gap of the thermoelectric study of argyrodites and contribute to a comprehensive understanding of the chemical bonding, lattice dynamics, and thermal transport of argyrodites.a potential for practical applications. Yet, it is still a challenge to decouple the adversely correlated {σ, S, κ e } toward high zT values via electronic and phonon band engineering. [3][4][5][6][7][8] Many efforts have been devoted to discover novel TE materials such as cage-like filled skutterudites (e.g., CeFe 4 Sb 12 , CoSb 3 , Sr 8 Ga 16 Ge 30 , etc.), [9][10][11][12] Zintl-phase compounds (e.g., CaZn 2 Sb 2 , Mg 3 Sb 2 , YbMg 2 Bi 2 , etc.), [13][14][15][16] and defective half-Heusler compounds (e.g., Nb 0.8 CoSb, Ti 0.9 NiSb, V 0.9 CoSb, etc.) [17] that possess a long-range order favoring charge carrier mobility while disordered in short range to inhibit heat-carrying phonons in the context of "phonon-glass-electron-crystal". [18] Recently, a class of "liquid-like" TE materials with complex phase transitions, ultralow lattice thermal conductivity, and liquidlike ionic conduction have been reported, Cu 2−x (S, Se, Te), [19][20][21] Ag 2 (S, Se, Te), [22,23] argyrodite, [24][25][26][27][28][29][30][31][32][33][34][35][36] AgCrSe 2 , [37,38] CuAgSe, [39] and AgCuTe [40] to name a few. Argyrodites are good examples of liquid-like TE materials. Argyrodites include 716, 816, and 916 phases in chemistry, with a general chemical formula A 12−n

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

\begin{array}{l} \frac{C_{P}}{T} = γ + β T^{2} + A {false(Θ_{E 1} false)}^{2} T^{- 3} \frac{e^{\frac{Θ_{E 1}}{T}}}{{(e^{\frac{Θ_{E 1}}{T}} - 1)}^{2}} + B {false(Θ_{E 2} false)}^{2} T^{- 3} \\ \frac{e^{\frac{Θ_{E 2}}{T}}}{{(e^{\frac{Θ_{E 2}}{T}} - 1)}^{2}} + C {false(Θ_{E 3} false)}^{2} T^{- 3} \frac{e^{\frac{Θ_{E 3}}{T}}}{{(e^{\frac{Θ_{E 3}}{T}} - 1)}^{2}} \end{array}

β = D (12 π^{4} N_{A} k_{B} / 5) {(Θ_{D})}^{- 3}

D = 1 - (A + B + C) / 3 N R

…”

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

m_{d}^{*}

m_{d}^{*} = N_{V}^{2 / 3} m_{b}^{*}

, where N V refers to both orbital and symmetry related degeneracy and

m_{b}^{*}

is the band effective mass.…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

High Thermoelectric Performance in Sulfide‐Type Argyrodites Compound Ag₈Sn(S₁₋_xSe_x)₆ Enabled by Ultralow Lattice Thermal Conductivity and Extended Cubic Phase Regime

Shen

Xia

Yang

et al. 2020

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Recent Advances in Liquid‐Like Thermoelectric Materials

Zhao

Qiu

Shi

et al. 2019

196

124

Thermoelectric technology has attracted great attention due to its ability to recover and convert waste heat into readily available electric energy. Among the various candidate materials, liquid‐like compounds have received tremendous research interest on account of their intrinsically ultralow lattice thermal conductivity, tunable electrical properties, and high thermoelectric performance. Despite their complex phase transitions and diverse crystal structures, liquid‐like materials have two independent sublattices in common: one rigid sublattice formed by immobile ions for the free transport of electrons and one liquid‐like sublattice consisting of highly mobile ions to interrupt the thermal transports. This review first outlines the common structural features of liquid‐like thermoelectrics, along with their unusual electron and phonon transport behaviors that well satisfy the concept of “phonon‐liquid electron‐crystal.” Next, some commonly adopted strategies for further improving their thermoelectric performance are highlighted. The main progress achieved in the typical liquid‐like TE materials is then summarized, with an emphasis on their diverse crystal structures, common characteristics, and unique transport properties. The recent understandings on the stability issue of liquid‐like TE materials are also introduced. Finally, an outlook is given for the liquid‐like materials with the aim to boost further development in this exciting scientific subfield.

Unlocking Ultralow Thermal Conductivity in α‐CuTeI via Specific Symmetry Breaking in Cu Sublattice

Yang,

Lin,

et al. 2024

Lattice softening is an intricate mechanism utilized to modulate lattice thermal conductivity (κlat). However, experimental observations are often complicated by numerous factors including thermal regimes, elemental matrices, and crystalline topographies, making the fundamental mechanisms complex. In this study, the temperature gradients are meticulously harnessed during phase transitions, both in heating and cooling trajectories, to ascertain that atomic configuration acts as the paramount factor modulating phonon propagation. Within CuTeI, the predilection between the tetragonal (β) and orthorhombic (α) phases is deftly manipulated via specific thermal pathways to a juncture of 273 K. A salient 44% variance in κlat is observed consequent to a singular alteration in the structural disposition of the bridging Cu atoms. Such atomic configurations delineate pronounced differential effects on the transmission dynamics of transverse and longitudinal phonons. The theoretical analysis indicates that the transverse acoustic velocity plays a more pivotal role in dictating κlat than its longitudinal counterpart due to its greater contribution to the Grüneisen parameter. The synergistic interplay of lattice softening and anharmonicity enhancement culminates in an exceptionally diminished κlat in α‐CuTeI, registering a record low κlat of 0.21 W/(m × K) among inorganic materials dominated by phonon–phonon scattering at 273 K. The revelations proffer avant‐garde perspectives for the nuanced modulation of phonon velocities and κlat.