High Porosity in Nanostructured n-Type Bi₂Te₃ Obtaining Ultralow Lattice Thermal Conductivity

Porous structure possesses full potentials to develop high-performance thermoelectric materials with low lattice thermal conductivity. In this study, the n-type porous nanostructured Bi₂Te₃ pellet is fabricated by sintering Bi₂Te₃ nanoplates synthesized with a facile solvothermal method. With adequate sublimations of Bi₂TeO₅ during the spark plasma sintering, homogeneously distributed pores and dense grain boundaries are successfully introduced into the Bi₂Te₃ matrix, causing strong phonon scatterings, from which an ultralow lattice thermal conductivity of <0.1 W m^-1 K^-1 is achieved in the porous nanostructured Bi₂Te₃ pellet. With the well-maintained decent electrical performance, a power factor of 10.57 μW cm^-1 K^-2 at 420 K, as well as the reduced lattice thermal conductivity, secured a promising zT value of 0.97 at 420 K, which is among the highest values reported for pure n-type Bi₂Te₃. This study provides the insight of realizing ultralow lattice thermal conductivity by synergistic phonon scatterings of pores and nanostructure in the n-type Bi₂Te₃-based thermoelectric materials.