Weak Electron–Phonon Coupling and Enhanced Thermoelectric Performance in n‐type PbTe–Cu₂Se via Dynamic Phase Conversion

Abstract

This study investigates Ga‐doped n‐type PbTe thermoelectric materials and the dynamic phase conversion process of the second phases via Cu2Se alloying. Introducing Cu2Se enhances its electrical transport properties while reducing its lattice thermal conductivity (κlat) via weak electron–phonon coupling. Cu2Te and CuGa(Te/Se)2 (tetragonal phase) nanocrystals precipitate during the alloying process, resulting in Te vacancies and interstitial Cu in the PbTe matrix. At room temperature, Te vacancies and interstitial Cu atoms serve as n‐type dopants, increasing the carrier concentration and electrical conductivity from ≈1.18 × 1019 cm−3 and ≈1870 S cm−1 to ≈2.26 × 1019 cm−3 and ≈3029 S cm−1, respectively. With increasing temperature, the sample exhibits a dynamic change in Cu2Te content and the generation of a new phase of CuGa(Te/Se)2 (cubic phase), strengthening the phonon scattering and obtaining an ultralow κlat. Pb0.975Ga0.025Te‐3%CuSe exhibits a maximum figure of merit of ≈1.63 at 823 K, making it promising for intermediate‐temperature device applications.

Unraveling the Role of Entropy in Thermoelectrics: Entropy-Stabilized Quintuple Rock Salt PbGeSnCdxTe3+x

“…The performance of thermoelectric materials is evaluated by the dimensionless figure of merit ZT , which is determined as ZT = S 2 σΤ/(κ e + κ L ) . Therefore, to obtain a high thermoelectric performance, a large Seebeck coefficient S and high electrical conductivity σ are desired, while the thermal conductivity κ, comprising the electronic contribution κ e and the lattice contribution κ L , should be minimized. − Over the past decades, several advanced thermoelectric materials have been found in the group IV–VI semiconductors, such as PbQ, − SnQ (Q = S, Se, and Te), − and GeTe. , Various strategies have been developed and successfully applied to optimize their thermoelectric performances, such as band convergence, − resonant level, , nanostructuring, ,− discordant atoms, − and intrinsically large anharmonicity, , and tremendous progress has been achieved. However, because of their binary composition and simple crystal structure, most of the developed group IV–VI semiconductors still exhibit a relatively high intrinsic thermal conductivity.…”

Two Mixed-Anion Semiconductors in the Ba–Sn–Te–S System with Low Thermal Conductivity

“…Thermoelectric materials can convert heat energy directly into electrical energy, which can be used to improve energy utilization efficiency in various fields. − The dimensionless figure of merit ZT determines the energy conversion efficiency of thermoelectric materials. The ZT is defined as ZT = (σ S 2 T )/κ, where σ represents the electrical conductivity, S represents the Seebeck coefficient, and T represents the working temperature in Kelvin. ,− κ is the total thermal conductivity, which includes the lattice thermal conductivity (κ lat ) and the carrier thermal conductivity (κ ele ). The high ZT of thermoelectric materials requires a high power factor (PF = σ S 2 ) and low total thermal conductivity κ. κ ele = L σ T = Lne μ T , where L represents the Lorenz number, n represents the carrier concentration, e represents the electron charge, and μ represents the carrier mobility, while the lattice thermal conductivity κ lat = 1/3 C V ν l , where C V represents the heat capacity, ν represents the phonon group velocity, and l represents the phonon mean free path. − Thus, the primary issue is that academics focus on the search for low κ lat in the field of thermoelectrics.…”

Ultra-Low Lattice Thermal Conductivity Enables High Thermoelectric Properties in Cu and Y Codoped SnTe via Multi-Scale Composite Nanostructures

“…Notable state-of-the-art thermoelectric materials include GeTe, , Bi 2 Te 3 , PbTe, Cu 2 Se, and SnSe, among others. Although their thermoelectric properties have been significantly improved, their applications are limited by many reasons, such as toxicity, limitations on the specific orientation of single crystals, sensitivity to phase transitions, and high cost.…”

“…As can be seen, an ideal thermoelectric material possesses both large power factor (S 2 σ) and low κ lat , which depend upon transports of phonons and charge carriers, respectively. 3−10 Notable state-of-the-art thermoelectric materials include GeTe, 11,12 Bi 2 Te 3 , 13 PbTe, 14 Cu 2 Se, 15 and SnSe, 16 among others. Although their thermoelectric properties have been significantly improved, their applications are limited by many reasons, such as toxicity, limitations on the specific orientation of single crystals, sensitivity to phase transitions, and high cost.…”