Enhancement of thermoelectric properties of p-type bismuth telluride bulk composites with AgTiO2 nano particles via spray coating and hot deformation process

We aimed to enhance p-type Bi_0.4Sb_1.6Te_3.4 (BST) composite's thermoelectric (TE) properties by minimizing thermal conductivity through hierarchical phonon scattering via nano Ag-coated TiO₂ (Ag/TiO₂). Hot deformation (HD) was employed to induce multi-scale microstructures in these high-performance p-type TE materials, affecting electrical and thermal transport properties through improved textures and donor-like effects. Our optimization strategy included creating grain boundaries, multiple phonons scattering centers, and introducing high-density lattice defects, significantly reducing lattice thermal conductivity. The combined effects led to a noticeable improvement in the figure of merit (zT) across the temperature range, with all TE parameters measured along the in-plane direction. In the case of the hot-deformed Bi_0.4Sb_1.6Te_3.4 alloy, the maximum zT reached 1.31 at 350 K, while the average zT (zT_avg) was 1.17 in the range of 300–400 K, suggesting promising potential for near room temperature TE power generation and solid-state cooling.