Enhanced thermoelectric properties of Cu-Se system via bond-structure adjustment by Ag-doping

Thermoelectric devices have shown attractive application prospects with the emergence of high performance thermoelectric materials in recent years. In the Cu-Se system, bond-structure adjustment was designed to improve thermoelectric properties through simple silver doping, which induces change of phase structure, energy band structure, and thermoelectric transport nature. The polycrystalline Cu2-xAgxSe bulk samples were prepared by the spark plasma sintering (SPS) following vacuum melting and grinding. Appropriate addition of silver makes alpha-Cu2Se lattice expansion, and beta-Cu2Se becomes the room temperature stable phase with further increase of the silver content (>=3%). Ag doping results in significant changes in valence band spectra, which improves thermoelectric transport behave in higher operation temperature. Due to the synergetic effect from electrical conductivity and Seebeck coefficient, the maximum power factor reaches 1456 mu Wm(-1)K(-2) at 773 K, which increases by 10% compared with the undoped sample. It is notable that the Cu1.99Ag0.01Se bulk sample achieve an low thermal conductivity of 1.1 W m(-1)K(-1) at 773 K, which can be attributed to enhancement of phonon scattering at different frequencies due to the diversified bond lengths and bond energy induced by Ag-doping. Benefiting from reduction of lattice thermal conductivity and enhancement of powder factor, the Cu1.99Ag0.01Se bulk sample shows the better TE transport properties and exhibits the highest ZT value similar to 1.12 at 773 K. (C) 2022 Elsevier B.V. All rights reserved.

Automated summary

With the emergence of high-performance thermoelectric materials, thermoelectric devices have shown attractive application prospects. In the Cu-Se system, bond-structure adjustment through simple silver doping has been designed to improve thermoelectric properties. The addition of silver expands the lattice of α-Cu2Se and stabilizes β-Cu2Se as the room temperature phase. Silver doping leads to significant changes in valence band spectra, improving thermoelectric transport behavior at higher temperatures. The Cu1.99Ag0.01Se bulk sample exhibits improved thermoelectric transport properties and demonstrates the highest ZT value at 773 K.