Enhanced thermoelectric and mechanical properties of Bi_0.5Sb_1.5Te₃ alloy with dispersed yttrium oxide ceramic nanoparticles

Reducing thermal conductivity while avoiding adverse interfacial reactions during sintering is crucial for improving the thermoelectric performance of Bi₂Te₃-based composites. Inert ceramic nanoparticles are good candidates for achieving this goal. In this study, we designed and prepared a series of p-type Bi_0.5Sb_1.5Te₃ nanocomposites decorated with Y₂O₃ ceramic nanoparticles via ball-milling dispersion and spark-plasma sintering. Owing to the chemical stability of the ceramics, no traces of atomic doping or interfacial reactions were observed. Transport measurements revealed that the Y₂O₃ nanoparticles distributed along the grain boundaries acted as energy-dependent carrier-filtering centers to improve the scattering parameter and Seebeck coefficient, contributing to the elevated power factor even with a decreased electrical conductivity. Moreover, the incorporated Y₂O₃ nanoparticles and various defect structures they induced effectively strengthened the phonon scattering and suppressed the lattice thermal conductivity. Consequently, a peak figure of merit (ZT) of 1.23 at 313 K was achieved for 0.4%Y₂O₃/Bi_0.5Sb_1.5Te₃, which is 13% higher than that of the matrix. In addition, the Vickers hardness of the composite material was 35% higher than that of the matrix. This study demonstrates the effectiveness of ceramic nanoparticles in synergistically improving the thermoelectric and mechanical properties, which may be further extended to other thermoelectric systems.