Vacancy controlled nanoscale cation ordering leads to high thermoelectric performance

Abstract

High thermoelectric performance is generally achieved in solid-solution alloyed or heavily doped semiconductors. The consequent atomic disorder has a trade-off in the thermoelectric figure of merit, zT: lattice thermal conductivity...

Stepwise Alloying in Liquid-like Solid Solutions to Achieve Crystallographic Distortion for Regulating Thermoelectric Transport Behavior

“…The diffraction spots generated by the nanoparticles in the Cu 1.9 Se matrix have been observed with unique different superperiodic structures, as schematically illustrated in Figure f,h, which was also demonstrated in a previous study . The lattice fringes in the grain boundary area became deformed and blurred, indicating the subsistence of large lattice distortion (marked as ⊥ ) in this area . This kind of dislocation usually resulted from the defects such as the mismatched impurity doped in Cu 2 Se, which are supposed to have great influence on TE performance for Cu 2– x Se materials.…”

“…31 The lattice fringes in the grain boundary area became deformed and blurred, indicating the subsistence of large lattice distortion (marked as ⊥ ) in this area. 32 This kind of dislocation usually resulted from the defects such as the mismatched impurity doped in Cu 2 Se, which are supposed to have great influence on TE performance for Cu 2−x Se materials. Collectively, the existing defects such as dense dislocations and phase boundary generated by the coalloying strategies could lead to the broadened diffraction peaks, as confirmed in Figure 1c.…”

Hg Doping Induced Reduction in Structural Disorder Enhances the Thermoelectric Performance in AgSbTe2

“…The cation disordered sublattice of rock salt AgSbTe 2 provides a unique opportunity to optimize the atomic disorder and consequently control the spontaneous formation of a nanoscale superstructure. Although spontaneous formation of the nanoscale superstructure has been observed in single-crystalline AgSbTe 2 , it is rare in its polycrystalline form. ,, Formation of the nanoscale superstructure due to enhanced cation ordering has recently been discovered as an efficient technique to reduce lattice thermal conductivity with a high zT in Cd doped AgSbTe 2 …”

“…However, the phase diagram of Sb 2 Te 3 –Ag 2 Te pseudobinary system indicates instability of stoichiometric AgSbTe 2 and its thermal decomposition into Ag 2 Te and Sb 2 Te 3 at relatively lower temperature (633 K) compared to its melting point. , As a consequence, a few earlier studies showed the congenital occurrence of the α-Ag 2 Te as a minor secondary phase in the AgSbTe 2 matrix in ambient condition irrespective of the various synthetic procedures applied. , The n-type conductivity of Ag 2 Te, just after the phase transition at ∼425 K, negatively affects the p-type conduction of the AgSbTe 2 matrix. ,, Therefore, augmenting the thermometric performance demands deterring the formation of Ag 2 Te as a secondary phase while synthesizing AgSbTe 2 . Recently, Cd, Se/S, and vacancy doping in AgSbTe 2 suppressed the formation of Ag 2 Te. Although, these doping reduced the κ lat in AgSbTe 2 , they also reduced the carrier mobility, which compromised the overall electronic transport.…”

High Thermoelectric Performance in Phonon‐Glass Electron‐Crystal Like AgSbTe2

“…[49][50][51] Because of the combined presence of low lattice thermal conductivity (0.6 Wm −1 K −1 at 300 K) [43] and flat degenerate valence bands in the electronic structure, AgSbTe 2 has proven to be a champion TE material. [4,45,52,53] However, there still exists ambiguities regarding the position of Ag/Sb in the cation sublattice in AgSbTe 2 , that is, whether the cations are fully disordered in the sub-lattice or a partial ordering is present, particularly at the nanoscale. [43,54] The disordered arrangement of cations significantly reduces the electrical conductivity and the formation of n-type 𝛼-Ag 2 Te second phase further reduces the ptype TE performance of AgSbTe 2 .…”