Enhanced thermoelectric properties of n-type Bi_2Te_3-based nanocomposite fabricated by spark plasma sintering

摘要

Highly dense n-type Bi_2Te_3-based thermoelectric materials dispersed with x vol.% γ-Al_2O_3 nanoparticles (x=0,0.4,1.0,1.5) were fabricated by spark plasma sintering method. The effects of γ-Al_2O_3 addition on microstructure and the thermoelectric properties were studied. It was found that γ-Al_2O_3 nanoparticles locate both at grain boundaries and inside Bi_2Se_0.3)Te_(2.7) 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 (ZT_(max)) reaches up to 0.99 for the sample with x=1.0 at 400 K, which is 35% improvement over the Bi_2Te_3-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.