AgCl Addition to Chalcopyrite Compound for Ultra-Low Thermal Conductivity in Realizing High ZT Thermoelectric Materials

Abstract

Optimizing the performance of thermoelectric materials by reducing its thermal conductivity is crucial to enhance its thermoelectric efficiency. Novel thermoelectric materials like the CuGaTe2 compound are hindered by high intrinsic thermal conductivity, which negatively impacts its thermoelectric performance. In this paper, we report that the introduction of AgCl by the solid-phase melting method will influence the thermal conductivity of CuGaTe2. The generated multiple scattering mechanisms are expected to reduce the lattice thermal conductivity while maintaining sufficient good electrical properties. The experimental results were supported by first-principles calculations confirming that the doping of the Ag will decrease the elastic constants, bulk modulus, and shear modulus of CuGaTe2, which makes the mean sound velocity and Debye temperature of Ag-doped samples lower than those of CuGaTe2, indicating the lower lattice thermal conductivity. In addition, the Cl elements within the CuGaTe2 matrix escaping during the sintering process will create holes of various sizes within the sample. These combined effects of holes and impurities will induce phonon scattering, which further reduces the lattice thermal conductivity. Based on our findings, we conclude that the introduction of AgCl into CuGaTe2 has shown a lower thermal conductivity without compromising the electrical performance, resulting in an ultra-high ZT value of 1.4 in the (CuGaTe2)0.96(AgCl)0.04 sample at 823 K.

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

“…The increasingly severe fossil fuel crisis and greenhouse effect are placing unprecedented pressure on energy supply. , Thermoelectric materials, due to their ability to mutually convert thermal energy into electrical energy, have garnered significant attention as they can efficiently convert industrial waste heat into electrical energy. , Typically, thermoelectric material properties were evaluated using the dimensionless parameter ZT = S 2 σ T /(κ l + κ e ), , where S represents the Seebeck coefficient, σ stands for the electrical conductivity, T is the absolute temperature, κ l is the lattice thermal conductivity, and κ e is the electronic thermal conductivity. , Achieving high ZT value necessitates elevated electrical conductivity and Seebeck coefficient, while maintaining relatively low thermal conductivity. − However, there exists a coupled relationship among S, σ, and κ e making it challenging to solely control any individual parameter. − Therefore, researchers have explored various methods for comprehensive control, such as adjusting carrier concentration and band engineering to improve electrical performance, − and implementing phonon engineering to reduce thermal conductivity. , …”