Improvement of power factor of n-type Bi2Te3 by dispersed nanosized Ga2Te3 precipitates

Abstract Inspired by the concept of energy filtering effect in improving the thermoelectric power factor ( PF ), we introduced a nanosized filter phase in an n-type Bi 2 Te 3 bulk material. We selected Ga 2 Te 3 as the filter phase because it has a suitable band offset at the conduction band minimum, as predicted by the first-principles calculations. We synthesized Bi 2 Te 3 containing Ga 2 Te 3 precipitates by carefully controlling the sintering and annealing temperatures, which followed the liquid-quenching process. It was found that the nanosized Ga 2 Te 3 precipitates (∼100 nm) improved the PF of n-type Bi 2 Te 3 , while the microsized Ga 2 Te 3 did not. In particular, the homogeneously dispersed nanosized Ga 2 Te 3 precipitates were better than the segregated Ga 2 Te 3 at the grain boundaries in improving the PF . The obtained PF of Bi 1.9 Ga 0.1 Te 3 at 300 K was 2.80 × 10 −3  W/mK 2 , which is 60% higher than that of n-type Bi 2 Te 3 . The Jonker plot clearly showed that this improvement is far beyond the optimized value for the given carrier concentration.