Improved Thermal Stability and Enhanced Thermoelectric Properties of p-Type BaCu₂Te₂ by Doping of Cl

Abstract

Doping in semiconductors is a widely implemented strategy for manipulation of carrier concentration, which is a critical parameter to regulate the thermoelectric performance. Stoichiometric BaCu 2 Te 2 shows high hole concentration and unstable transport properties owing to the inherent Cu vacancy and dynamic precipitation behavior. In this work, Te has been partially substituted by Cl in BaCu 2 Te 2 to suppress the overhigh hole concentration. Due to the high electronegativity of Cl, strong Cl−Cu bonds can significantly inhibit the Cu migration and the consequent dynamic precipitation. Meanwhile, nanoprecipitate BaCl 2 distributes in the grain boundary, acting as ionic blocking layers. Therefore, the thermal stability of the samples can be essentially improved via chemical bonding strengthening and grain boundary engineering. In terms of thermal transport, the introduced point defects and second phase strengthen the short-wavelength and medium-wavelength phonon scattering, leading to further reduced thermal conductivity. Eventually, the repeatable ZT value of BaCu 2 Te 1.98 Cl 0.02 reached 1.22 at 823 K, which is higher by 19.6% compared with 1.02 of pristine BaCu 2 Te 2 . The average ZTs of BaCu 2 Te 2−x Cl x (x = 0, 0.02, 0.04, and 0.06) in the temperature range of 323−823 K are 0.737 for x = 0.02, 0.689 for x = 0.04, and 0.667 for x = 0.06, which are 24.6, 17.2, and 13.4% higher than the average ZT of 0.588 corresponding to the undoped sample, respectively. The study shows that synergetic enhancements of thermal stability and thermoelectric properties can be achieved by strengthening chemical bonding and constructing ionic blocking layers in the grain boundary, which can be applied to other fast-ionic conductor thermoelectric materials.

Syntheses and characterization of two new layered ternary chalcogenides NaScQ2 (Q = Se and Te)

“…3c). The observed total thermal conductivity values of these samples at 673 K are comparable with a few well-known transition metal containing thermoelectric chalcogenides such as Ba 0.925 Na 0.075 Cu 2 Se 2 (∼0.75 W m −1 K −1 at 675 K), 62 BaCu 2 Te 2 (∼0.85 W m −1 K −1 at 675 K), 63 and Cu 2 Se (∼0.9 W m −1 K −1 at 480 K). 64…”

Thermoelectric Performance Enhancement in Commercial Bi0.5Sb1.5Te3 Materials by Introducing Gradient Cu-Doped Grain Boundaries

“…Moreover, the calculated frequency-dependent phonon scattering process is also present in Figure d. The result suggests that the introduced point defects scattered high-frequency phonons, the dislocation and nanostructures scattered middle-frequency phonons, and the abundant grain boundaries scattered low-frequency phonons. , Therefore, the low κ latt in the as-prepared sample can be attributed to the combination phonon scattering effects of multiscale hierarchical scattering architectures. − …”

The Substitution of Rare-Earth Gd in BaScCuTe3 Realizing the Band Degeneracy and the Point-Defect Scattering toward Enhanced Thermoelectric Performance

“…These compounds have attracted significant research interest as promising thermoelectric materials, , since Zintl compounds possessing these structural features align with the concept of ‘electron-crystal, phonon-glass’ (PEGC), wherein the electronic properties mimic a crystalline structure, while the phonon behavior bears resemblance to an amorphous or glassy structure . Over the past few decades, a variety of Zintl compounds have been extensively investigated as potential thermoelectric materials, including the 1–2–2 type, − 14–1–11 type, ABX (A = Alkali metal, B = Alkaline earth metal or Zn, Cd, X = Group VA element), − 9–4–9 type, and 2–1–2 type, among others.…”