Comparative PECS and LPBF Processing of Bi0.5Sb1.5Te3: Microstructure, Texture, and Thermoelectric Performance

Abstract

Laser powder bed fusion (LPBF) is emerging as a promising manufacturing route for next-generation thermoelectric generators, offering unprecedented freedom in the fabrication of complex device geometries. However, the rapid melting and solidification inherent to LPBF produce microstructures fundamentally different from those of conventional consolidation techniques, and how these processing-induced features affect thermoelectric performance remains poorly understood. In this work, LPBF-produced p-type Bi0.5Sb1.5Te3 was compared with materials fabricated by pulsed electric current sintering (PECS), which served as a reference processing route providing a higher degree of crystallographic texture. The comparison enabled identification of the microstructural characteristics governing electrical and thermal transport. In particular, the investigated materials exhibited a wide range of preferred orientation (Lotgering factor F ≈ 0.02–0.20), while maintaining comparable Seebeck coefficients (∼160–175 μV K–1). In contrast, electrical conductivity (720–2200 S cm–1 at 300 K), thermal conductivity (0.9–1.5 W m–1 K–1), and consequently the thermoelectric figure of merit varied strongly with the processing route and crystallographic orientation. PECS samples with moderate preferred orientation reached ZT ≈ 1.1, while LPBF specimens exhibited ZT ≈ 0.4–0.5. The lower LPBF performance reflects weaker texture and processing-induced defects, partly related to nonideal powder morphology and feeding conditions. Additionally, numerical modeling (FEM) was performed to evaluate energy conversion efficiency, demonstrating higher output power and overall efficiency for the PECS samples compared to the LPBF ones. The comparative analysis demonstrates that crystallographic texture and microstructural integrity are key factors affecting thermoelectric performance and identifies processing-related limitations under the LPBF conditions investigated in this study.