Ultralow Lattice Thermal Conductivity in SnTe by Incorporating InSb

Optimizing Thermoelectric Properties through Compositional Engineering in Ag-Deficient AgSbTe2 Synthesized by Arc Melting

Thermoelectric materials offer a promising avenue for energy management, directly converting heat into electrical energy. Among them, AgSbTe2 has gained significant attention and continues to be a subject of research at further improving its thermoelectric performance and expanding its practical applications. This study focuses on Ag-deficient Ag0.7Sb1.12Te2 and Ag0.7Sb1.12Te1.95Se0.05 materials, examining the impact of compositional engineering within the AgSbTe2 thermoelectric system. These materials have been rapidly synthesized using an arc-melting technique, resulting in the production of dense nanostructured pellets. Detailed analysis through scanning electron microscopy (SEM) reveals the presence of a layered nanostructure, which significantly influences the thermoelectric properties of these materials. Synchrotron X-ray diffraction reveals significant changes in the lattice parameters and atomic displacement parameters (ADPs) that suggest a weakening of bond order in the structure. The thermoelectric characterization highlights the enhanced power factor of Ag-deficient materials that, combined with the low glass-like thermal conductivity, results in a significant improvement in the figure of merit, achieving zT values of 1.25 in Ag0.7Sb1.12Te2 and 1.01 in Ag0.7Sb1.12Te1.95Se0.05 at 750 K.

Improving thermoelectric performance by constructing a SnTe/ZnO core-shell structure

SnTe is becoming a new research focus as an intermediate temperature thermoelectric material for its environment-friendly property. Herein, the SnTe/ZnO core-shell structure prepared by a facile hydrothermal method is firstly constructed to enhance the thermoelectric performance. The characterization results demonstrate that ZnO nanosheets are coated on the surface of SnTe particles by in situ synthesis and converted into ZnO nano-dots by spark plasma sintering. The energy barriers built by the SnTe/ZnO core-shell structure improve the Seebeck coefficient effectively. Additionally, the increased density of interfaces induced by ZnO can effectively scatter low/medium frequency phonons, reducing the lattice thermal conductivity in the low/medium temperature region. Further, the point defects caused by Cu2Te-alloying strengthen the scattering of high frequency phonons. The lattice thermal conductivity reaches 0.48 W m-1 K-1, which is close to the amorphous limit of pristine SnTe. As a result, a peak ZT value of 0.94 is achieved at 823 K for SnTe(Cu2Te)0.06-1.5% ZnO, benefiting from the synergistic optimization of thermal and electrical properties. This provides a new idea for exploring an optimization strategy of thermoelectric performance.

Enhanced Thermoelectric Performance of SnTe-Based Materials via Interface Engineering

Interface engineering has been regarded as an effective strategy to improve thermoelectric (TE) performance by modulating electrical transport and enhancing phonon scattering. Herein, we develop a new interface engineering strategy in SnTe-based TE materials. We first use a one-step solvothermal method to synthesize SnTe powders decorated by Sb₂Te₃ nanoplates. After subsequent spark plasma sintering, we found that an ion-exchange reaction between the Sb₂Te₃ and SnTe matrixes happens to result in Sb doping and the formation of SnSb nanoparticles and the recrystallization of the nanograined SnTe at the grain boundaries of the SnTe matrix. Benefitting from this unique engineering, a significantly reduced lattice thermal conductivity of ∼0.64 W m^-1 K^-1 and a high zT of ∼1.08 (∼100% enhanced) at 873 K are achieved in SnTe-Sb_0.06. Such improved TE properties are attributed to the optimized carrier concentration and valence band convergence due to the Sb doping and enhanced phonon scattering by interface engineering at the grain boundaries. This work has demonstrated a facile and effective method to realize high-TE-performance SnTe via interface engineering.

Electronic, optical, and thermoelectric properties of Janus In-based monochalcogenides

Inspired by the successfully experimental synthesis of Janus structures recently, we systematically study the electronic, optical, and electronic transport properties of Janus monolayers In₂XY(X/Y= S, Se, Te withX≠Y) in the presence of a biaxial strain and electric field using density functional theory. Monolayers In₂XYare dynamically and thermally stable at room temperature. At equilibrium, both In₂STe and In₂SeTe are direct semiconductors while In₂SSe exhibits an indirect semiconducting behavior. The strain significantly alters the electronic structure of In₂XYand their photocatalytic activity. Besides, the indirect-direct gap transitions can be found due to applied strain. The effect of the electric field on optical properties of In₂XYis negligible. Meanwhile, the optical absorbance intensity of the Janus In₂XYmonolayers is remarkably increased by compressive strain. Also, In₂XYmonolayers exhibit very low lattice thermal conductivities resulting in a high figure of meritZT, which makes them potential candidates for room-temperature thermoelectric materials.

Role of anharmonic strength and number of allowed three-phonon processes in lattice thermal conductivity of SnTe based compounds

The lattice heat transport properties of the thermoelectric (TE) material SnTe and the doped Sn₇SbTe₈ and Sn₇BiTe₈ are examined using Boltzmann transport theory supplemented with first-principle calculations. We illustrate the microscopic origin of the lattice thermal conductivity, κ _l of the materials by calculating the mode Grüneisen parameters, phase space volume for three-phonon processes, the anharmonic scattering rates (SR), and the phonon group velocities. SnTe is found to be a low κ _l material with a value of ∼3 W mK^-1 at room temperature in agreement with experiments. The phonon scatterings in pristine SnTe mainly originates in the strong anharmonicity of the material, as evidenced by the large values of its mode Grüneisen parameters. Doping with Sb or Bi reduces the anharmonic strength. For Sb doped Sn₇SbTe₈, it results in a drop in the SR and hence a higher κ _l value. However in the Bi doped Sn₇BiTe₈, the number of allowed three-phonon processes gets greatly enhanced which compensates for the reduction in anharmonicity. This coupled with lower phonon group velocities lowers the κ _l value for the Bi doped system below that of pristine SnTe. In nanowire structures, κ _l values for the doped systems get drastically reduced yielding an ultra-low value of 0.84 W mK^-1 at 705 K for the Bi doped material for a nanowire of 10 nm diameter.

Enhancing the thermoelectric properties of SnTe via introducing PbTe@C core-shell nanostructures

SnTe is an emerging IV-VI metal chalcogenide, but its low Seebeck coefficient and high thermal conductivity mainly originating from the high hole concentration limit its thermoelectric performance. In this work, an amorphous carbon core-shell-coated PbTe nanostructure prepared by a "bottom-up" method is first incorporated into the Sn1-ySbyTe matrix to enhance the thermoelectric performance of SnTe. The square-like PbTe nanoparticles maintain their original cubic morphology and do not grow up obviously after the SPS process due to the coating of the C layer, bringing about the formation of nanopores locally, while Sb alloying induces Sb point defects and Sb-rich precipitates. All these unique hierarchical microstructures finally lead to an ultralow lattice thermal conductivity (∼0.48 W-1 m-1 K-1) approaching amorphous limits (∼0.40 W-1 m-1 K-1). In addition, the incorporation of PbTe@C core-shell nanostructures decreases the carrier mobility obviously with a slight loss in carrier concentration, resulting in the deterioration of electrical properties to a certain extent. As a result, a peak thermoelectric figure of merit (ZT) of 1.07 is achieved for Sn0.89Sb0.11Te-5%PbTe@C at 873 K, which is approximately 154.76% higher than that of pristine SnTe. This work provides a new strategy to enhance the thermoelectric performance of SnTe and also offers a new insight into other related thermoelectric systems.

Achieving Enhanced Thermoelectric Performance in (SnTe)1-x(Sb2Te3)x and (SnTe)1-y(Sb2Se3)y Synthesized via Solvothermal Reaction and Sintering

SnTe is proposed to be an intriguing low-toxicity alternative to PbTe. Herein, we report the diminished lattice thermal conductivity (κ_L) and enhanced zT of SnTe by way of vacancy engineering. (SnTe)_1-x(Sb₂Te₃)_x (x = 0.03, 0.06, and 0.10) and (SnTe)_1-y(Sb₂Se₃)_y (y = 0.03 and 0.06) were synthesized by blending and sintering their solution-synthesized nano/microstructures (i.e., SnTe octahedral particles, Sb₂Te₃ nanoplates, and Sb₂Se₃ nanorods). Benefiting from the chemical reactions during sintering, single-phase SnTe-based solid solutions were formed when x or y is not higher than 0.06, into which tunable concentrations of Sn vacancies were introduced. Such vacancies significantly enhance phonon scattering, leading to the sharply reduced room temperature κ_L of 1.40 and 1.26 W m^-1 K^-1 for x = 0.06 and y = 0.06 samples, respectively, as compared to 3.73 W m^-1 K^-1 for pristine SnTe. Enabled by point defects with the highest concentration and SnSb₂Te₄ secondary phase, (SnTe)_0.90(Sb₂Te₃)_0.10 sample obtains the lowest κ_L of 0.70 W m^-1 K^-1 at 813 K. Ultimately, maximum zT values of 0.6 and 0.7 at 813 K are achieved in (SnTe)_0.90(Sb₂Te₃)_0.10 and (SnTe)_0.94(Sb₂Se₃)_0.06, respectively. This study demonstrates the effectiveness of vacancy engineering in improving zT of SnTe-based materials.