Design of Domain Structure and Realization of Ultralow Thermal Conductivity for Record‐High Thermoelectric Performance in Chalcopyrite

Abstract

Chalcopyrite compound CuGaTe2 is the focus of much research interest due to its high power factor. However, its high intrinsic lattice thermal conductivity seriously impedes the promotion of its thermoelectric performance. Here, it is shown that through alloying of isoelectronic elements In and Ag in CuGaTe2, a quinary alloy compound system Cu1−xAgxGa0.4In0.6Te2 (0 ≤ x ≤ 0.4) with complex nanosized strain domain structure is prepared. Due to strong phonon scattering mainly by this domain structure, thermal conductivity (at 300 K) drops from 6.1 W m−1 K−1 for the host compound to 1.5 W m−1 K−1 for the sample with x = 0.4. As a result, the optimized chalcopyrite sample Cu0.7Ag0.3Ga0.4In0.6Te2 presents an outstanding performance, with record‐high figure of merit (ZT) reaching 1.64 (at 873 K) and average ZT reaching 0.73 (between ≈300 and 873 K), which are ≈37 and ≈35% larger than the corresponding values for pristine CuGaTe2, respectively, demonstrating that such domain structure arising from isoelectronic multielement alloying in chalcopyrite compound can effectively suppress its thermal conductivity and elevate its thermoelectric performance remarkably.

High Entropy Semiconductor AgMnGeSbTe4 with Desirable Thermoelectric Performance

“…The electrical conductivity of AgMnGeSbTe 4 decreases from 259 S cm −1 at 300 K to 180 S cm −1 at 600 K, showing a degenerate semiconductor behavior. Then, the electrical conductivity rises to 294 S cm −1 at 773 K because of the intrinsic excitation (a common phenomenon in semiconductors with a narrow band gap [ 25–27 ] ). Hall measurements (Figure 4b) show that the AgMnGeSbTe 4 has a hole concentration of 8.10 × 10 19 cm −3 at room temperature, indicating it is a p‐type semiconductor, in good agreement with the positive sign of the Seebeck coefficients shown below.…”

“…The electrical conductivity of AgMnGeSbTe 4 decreases from 259 S cm −1 at 300 K to 180 S cm −1 at 600 K, showing a degenerate semiconductor behavior. Then, the electrical conductivity rises to 294 S cm −1 at 773 K because of the intrinsic excitation (a common phenomenon in semiconductors with a narrow band gap [25][26][27] ).…”

Features of crystal structures and thermo‐mechanical properties of weberites RE3NbO7 (RE=La, Nd, Sm, Eu, Gd) ceramics

“…The management of heat conduction is vital for various materials and applications 37‐40 . To understand the heat transport mechanism and tailor thermal conductivity of weberites RE 3 NbO 7 , the connections between heat conduction and mechanical properties (acoustic velocity and Young's modulus) are built.…”

“…The management of heat conduction is vital for various materials and applications. [37][38][39][40] To understand the heat transport mechanism and tailor thermal conductivity of weberites RE 3 NbO 7 , the connections between heat conduction and mechanical properties (acoustic velocity and Young's modulus) are built. Figure 6A shows that the limit thermal conductivities (k min ) increases with the decreasing RE 3+ ionic radius, as they are proportional to acoustic velocity 39 : where k B is the Boltzmann constant, n is atomic number per unit cell, when V L and V T are longitudinal and transverse acoustic velocities, respectively.…”

Effects of sintering temperature on thermoelectric properties of Cu1.8S bulk materials

“…The crystal structure of Cu 1.8 S is comparable to that of Cu 2 S, except that only 9/10 of the copper atoms are occupied [38]. As a superionic conductor, Cu 1.8 S is often used as conductive fibers due to Cu ions have high mobility [39]. But Cu 1.8 S has a low Seebeck coefficient, leading to powders factor reduction, so it has received little attention [40].…”