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.