Hierarchical Structuring to Break the Amorphous Limit of Lattice Thermal Conductivity in High-Performance SnTe-Based Thermoelectrics

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.

Zinc Doping Induces Enhanced Thermoelectric Performance of Solvothermal SnTe

The creation of hierarchical nanostructures can effectively strengthen phonon scattering to reduce lattice thermal conductivity for improving thermoelectric properties in inorganic solids. Here, we use Zn doping to induce a remarkable reduction in the lattice thermal conductivity in SnTe, approaching the theoretical minimum limit. Microstructure analysis reveals that ZnTe nanoprecipitates can embed within SnTe grains beyond the solubility limit of Zn in the Zn alloyed SnTe. These nanoprecipitates result in a substantial decrease of the lattice thermal conductivity in SnTe, leading to an ultralow lattice thermal conductivity of 0.50 W m-1 K-1 at 773 K and a peak ZT of ~0.48 at 773 K, marking an approximately 45 % enhancement compared to pristine SnTe. This study underscores the effectiveness of incorporating ZnTe nanoprecipitates in boosting the thermoelectric performance of SnTe-based materials.

Achieving High Thermoelectric Performance in ZnSe-Doped CuGaTe2 by Optimizing the Carrier Concentration and Reducing Thermal Conductivity

The CuGaTe2 thermoelectric material has garnered widespread attention as an inexpensive and nontoxic material for mid-temperature thermoelectric applications. However, its development has been hindered by its low intrinsic carrier concentration and high thermal conductivity. This study investigates the band structure and thermoelectric properties of (CuGaTe2)1-x (ZnSe)x (x = 0, 0.25%, 0.5%, 1%, 1.5%, and 2%). The research revealed that the incorporation of Zn and Se atoms enhanced the level of band degeneracy and electron density of states near Fermi level, significantly raising carrier concentration through the formation of Zn Ga - point defects. Simultaneously, when the doping content reached 1.5%, the ZnTe second phase emerged, collaborating with point defects and high-density dislocations, effectively scattering phonons and substantially reducing lattice thermal conductivity. Therefore, introducing ZnSe can simultaneously optimize the material's electrical and thermal transport properties. The (CuGaTe2)0.985(ZnSe)0.015 sample reaches peak ZT of 1.32 at 823 K, representing a 159% increase compared to pure CuGaTe2.

Study on lattice dynamics and thermal conductivity of fluorite AF2 (A = Ca, Sr, Ba) based on first principles calculations

Fluorite materials have received particular attention in electron optics due to their favorable optical properties. However, further exploration of these materials in the thermoelectric (TE) field is hampered by the lack of studies on their lattice thermal transport properties. In this work, we use first-principles calculations, combined with self-consistent phonon theory, compressive sensing lattice dynamics and the Boltzmann transport equation, to study the microscopic mechanism of lattice thermal transport properties in AF2 (A = Ca, Sr, Ba) with a fluorite structure. We investigate the effects of three-phonon and four-phonon scattering and quartic anharmonic renormalization of phonon frequencies on this system. The results show that the bonding strength of atoms A (Ca, Sr, and Ba) plays an important role in the thermal transport process, and the third-order anharmonicity also plays an important role in this system. Meanwhile, the role of the quartic anharmonicity cannot be ignored. Our findings not only fill in the gaps in the study of lattice thermal transport of fluorite materials, but also deepen the comprehensive understanding of the high κL value of fluorite materials.

Bottom-Up Synthesis of SnTe-Based Thermoelectric Composites

There is a need for the development of lead-free thermoelectric materials for medium-/high-temperature applications. Here, we report a thiol-free tin telluride (SnTe) precursor that can be thermally decomposed to produce SnTe crystals with sizes ranging from tens to several hundreds of nanometers. We further engineer SnTe-Cu₂SnTe₃ nanocomposites with a homogeneous phase distribution by decomposing the liquid SnTe precursor containing a dispersion of Cu_1.5Te colloidal nanoparticles. The presence of Cu within the SnTe and the segregated semimetallic Cu₂SnTe₃ phase effectively improves the electrical conductivity of SnTe while simultaneously reducing the lattice thermal conductivity without compromising the Seebeck coefficient. Overall, power factors up to 3.63 mW m^-1 K^-2 and thermoelectric figures of merit up to 1.04 are obtained at 823 K, which represent a 167% enhancement compared with pristine SnTe.