Thermoelectric Performance of Surface-Engineered Cu_1.5–xTe–Cu₂Se Nanocomposites

Abstract

Cu2–x S and Cu2–x Se have recently been reported as promising thermoelectric (TE) materials for medium-temperature applications. In contrast, Cu2–x Te, another member of the copper chalcogenide family, typically exhibits low Seebeck coefficients that limit its potential to achieve a superior thermoelectric figure of merit, zT, particularly in the low-temperature range where this material could be effective. To address this, we investigated the TE performance of Cu1.5–x Te–Cu2Se nanocomposites by consolidating surface-engineered Cu1.5Te nanocrystals. This surface engineering strategy allows for precise adjustment of Cu/Te ratios and results in a reversible phase transition at around 600 K in Cu1.5–x Te–Cu2Se nanocomposites, as systematically confirmed by in situ high-temperature X-ray diffraction combined with differential scanning calorimetry analysis. The phase transition leads to a conversion from metallic-like to semiconducting-like TE properties. Additionally, a layer of Cu2Se generated around Cu1.5–x Te nanoparticles effectively inhibits Cu1.5–x Te grain growth, minimizing thermal conductivity and decreasing hole concentration. These properties indicate that copper telluride based compounds have a promising thermoelectric potential, translated into a high dimensionless zT of 1.3 at 560 K.

Ion transport induced room-temperature insulator–metal transition in single-crystalline Cu2Se

“…These results show that Cu 2 Se can be a prototypical material for studying ion-mediated IMT and is promising for applications beyond thermoelectrics. 2,20,49,50…”

Room-Temperature Synthesis and Low Thermal Conductivity in Nanocrystalline Ag3CuS2

“…Ag- and Cu-based chalcogenides, chalco-halides, and halide materials show structural phase transitions, a high degree of disorder, and ion dynamics. , In recent years, many Ag- and Cu-based chalcogenide compounds have been synthesized by low-temperature soft chemical solvothermal and hot injection methods. A few examples include Ag 2 Se, Ag 2 Te, Cu 2 Se, and Cu 2 Te and their composites, as well as ternary Ag 3 AuSe 2 , CuAgSe, and AgCuS. ,,,,− The wet chemical synthesis of materials created a great scope for modification of the physical properties of materials by controlling the crystal structure, size, morphology, increased surface states, and grain boundary. For instance, p–n–p -type conduction switching behavior for AgBiSe 2 was observed only in the nanocrystalline form, whereas for AgCuS conduction switching was observed in the bulk form. − ,− Herein, we report a room-temperature and atmospheric-pressure synthesis of Ag 3 CuS 2 semiconductor nanocrystals, along with their characterization and thermal transport properties.…”

Combined Defect and Heterojunction Engineering in ZnTe/CoTe2@NC Sulfur Hosts Toward Robust Lithium–Sulfur Batteries

“…Nevertheless, TMTs offer several patent advantages over the wide variety of tested compounds that, if used in very small quantities, could help balance and potentially overcome their drawbacks. These advantages include i) much higher electrical conductivities (e.g., 1.15 × 10 6 S m −1 for NiTe 2 ) compared with oxides, sulfides, and selenides counterparts (e.g., 0.55 S m −1 for NiS 2 ), [11] and ii) high catalytic activities related to the metal cation (Co 2+ , Zn 2+ , and Ni 2+ ) forming an octahedral complex with Te 2 2− in a low-spin state, while the metal 3d orbital splits into two subordinate orbitals, t 2g and e g . In TMTs, the metal ions adopt different spin modes in the 3D electronic configuration, which can promote the rapid charge transfer of the electrode and the LiPS conversion.…”