Enhanced thermoelectric properties of Bi0.5Sb1.5Te3 composites with in-situ formed senarmontite Sb2O3 nanophase

A lot of efforts being invested into producing efficient thermoelectric devices based on Bi0.5Sb1.5Te3 materials for room temperature applications. Key research achievements of these efforts that incorporation of oxide nanoparticles into Bi0.5Sb1.5Te3 materials exhibit higher thermoelectric performance in nano-composite form. Here, we prepared Bi0.5Sb1.5Te3 nanocomposite incorporated with TeO2 nanoparticles (NPs) by high energy ball milling and spark plasma sintering, where in-situ Sb2O3 phase and triple functional interfaces were developed. The formation mechanism of in-situ Sb2O3 phase in the Bi0.5Sb1.5Te3/TeO2 composites was explored by the thermodynamic calculations; microstructural features and material composition in the bulk samples were investigated using high-resolution transmission electron microscopy (HRTEM) coupled with energy dispersive X-ray spectroscopy (EDS). The formation of interfaces between in situ senarmontite Sb2O3 nanophase and Bi0.5Sb1.5Te3 matrix causes an enhanced Seebeck coefficient by ∼20% due to increase of carrier energy filtering and significant reduction of thermal conductivity by ∼77% ascribed to intensified phonon scattering or trapping at 350 K. As a result, an improved dimensionless figure of merit (ZT) of 1.07 at 350 K was achieved in a Bi0.5Sb1.5Te3/3 wt%TeO2 composites. The proposed in-situ reaction and interface formation mechanisms are expected to open the possibility of further increases in ZT.