Effects of Microstructure and Neodymium Doping on Bi2Te3 Nanostructures: Implications for Thermoelectric Performance

We report on an intriguing aspect of the effects of microstructure and chemistry on thermoelectric (TE) transport properties of nanostructured Bi2Te3-based compounds that are associated with their topologically insulating (TI) nature. Nanograined n-type Bi2Te3 and Bi1.94Nd0.06Te3 samples were consolidated by uniaxial hot pressing of nanoparticles (NPs) produced by solution synthesis. The grain size was controlled by changing the duration of the hot-pressing process. We found that the room-temperature values of electrical conductivity, Seebeck coefficient, and charge carrier mobility of the consolidated Bi2Te3 samples increase with the reduction of the average grain size. This phenomenon was observed earlier for Bi2Se3, which is a well-known TI material. We also found that Nd-doping reduces the electrical conductivity, Seebeck coefficient, charge carrier mobility, and thermal conductivity near room temperature (310 K). Interestingly, Nd-doping reverses the dependence of mobility on grain size compared to undoped Bi2Te3, which is associated with its magnetic moment. These observations can be utilized for further enhancement of the TE power factor of bulk nanograined TE materials to be applied for power generation near room temperature as well as cooling, in addition to the positive effect on reducing thermal conductivity due to phonon scattering.

Automated summary

The experiment showed that the electrical conductivity, Seebeck coefficient, and charge carrier mobility of the Bi2Te3 samples increase with the reduction of grain size, while Nd-doping reduces these properties and reverses the dependence of mobility on grain size compared to undoped Bi2Te3.