Enhanced thermoelectric properties of n-type Bi2Te3-based nanocomposite fabricated by spark plasma sintering

Highly dense n-type Bi2Te3-based thermoelectric materials dispersed with x vol.% γ-Al2O3 nanoparticles (x = 0, 0.4, 1.0, 1.5) were fabricated by spark plasma sintering method. The effects of γ-Al2O3 addition on microstructure and the thermoelectric properties were studied. It was found that γ-Al2O3 nanoparticles locate both at grain boundaries and inside Bi2Se0.3Te2.7 grains. The nanoparticles induce both potential barrier scattering effect and additional phonon scattering effect, which simultaneously enhance the Seebeck coefficient and reduce the lattice thermal conductivity of the nanocomposites in the measured temperature range of 300–500 K, respectively. The maximum dimensionless figure of merit (ZTmax) reaches up to 0.99 for the sample with x = 1.0 at 400 K, which is 35% improvement over the Bi2Te3-based matrix. More importantly, the average ZT value of the sample increases from 0.65 to 0.91 in the temperature range 300–500 K, making the nanocomposites much more applicable in cooling and power generation.

Research highlights
► n-Type γ-Al2O3-dispersed Bi2Se0.3Te2.7 nanocomposites were fabricated by spark plasma sintering.
► The nanophase distribute at grain boundary and inside the matrix.
► The introduction of γ-Al2O3 nanoparticles simultaneously enhances the Seebeck coefficient and reduces the thermal conductivity.
► The ZTmax reaches up to 0.99 for the sample with x = 1.0, being 35% improvement over the matrix.