Cu-Intercalated and Structurally Tailored Layered Bi_0.5Sb_1.5Te₃ Achieves Enhanced Power Factor and Thermoelectric ZT

Conventional Cu doping in Bi_0.5Sb_1.5Te₃ relies on high-temperature alloying, which tunes carrier concentration but also introduces structural disorder that degrades mobility and limits thermoelectric performance. To overcome this issue, a thermally driven Cu intercalation approach is developed that inserts Cu atoms into the van der Waals (vdW) gaps and employs spark plasma sintering (SPS) to form a well-textured architecture. Cu intercalation modifies the interlayer registry, while SPS-induced basal-plane alignment preserves single-crystal-like anisotropic transport and mitigates the cleavage fragility of the layered structure. The resulting microstructure, featuring aligned lamellae and subtle lattice distortions, facilitates anisotropic carrier conduction and enhances phonon scattering. Consequently, the carrier mobility increases from 158 to 287 cm² V^-1 s^-1, the power factor reaches ≈60.6 µW cm^-1 K^-2, and the lattice thermal conductivity is suppressed, as supported by Debye-Callaway analysis. A peak figure of merit (ZT) of ≈1.6 at 370 K is achieved, ≈70% higher than that of the non-intercalated counterpart. This work establishes Cu intercalation combined with SPS texturing as a decisive materials-preparation route and a broadly applicable strategy for layered materials, enabling concurrent enhancement of charge transport and mechanical robustness.