Mobility-enhanced thermoelectric performance in textured nanograin Bi2Se3, effect on scattering and surface-like transport

We report on the effect of artificially generated textures of Bi 2 Se 3 in thermoelectric performance and low-temperature magnetoresistance. A set of texturized nanograined Bi 2 Se 3 samples was investigated, ranging from predominantly c -axis texture to random texture. c -axis oriented layered domains rendered the samples highly conducting due to drastically enhanced mobility, up to 1600 cm 2 V −1 s −1 at low temperature, and enhanced both carrier concentration and electrical conductivity. The largest power factor of 800 μWm −1 K −2 and highest z T ≈ 0.14 both at 300K were observed in a sample with a predominantly layered and c-axis oriented texture. The random texture reduced the thermal conductivity, while the Seebeck coefficient showed no particular correlation with the texture. We have shown that the milling procedure generated a higher degree of disorder by increasing the milling frequency. As a result, the carrier scattering mechanism in the samples changed from mostly electron-phonon interaction at 5Hz to disorder-related scattering at 10Hz and 20Hz milling frequency. The weak antilocalization effect was observed in the magnetoresistance of pressed samples with different textures, pointing towards surface-like transport channels. The Hikami-Larkin-Nagaoka (HLN) model was used to evaluate the phase coherence length, resulting in a high value of roughly 600 nm regardless of the texture. However, a larger number of surface-like transport channels was obtained for the samples with random texture. • Ball milling allows to change grain structure from oriented-layered to random-fine grain. • High mobility obtained in layered texture samples. • Electron scattering mechanisms change form electron-phonon to disorder driven as texture becomes random. • zT increases in layered samples due to increased mobility and carrier concentration. • Weak antilocalization effect is measurable in random textured samples because of bulk channel suppression.