Promoted thermoelectric performance of (Ag, Na) co-doped polycrystalline BiSe by optimizing the thermal and electrical transports simultaneously

Abstract

Listen

Translate article

BiSe has recently emerged as a new promising Te-free thermoelectric material due to its superlattice structure and intrinsic low thermal conductivity. However, the inherent high carrier concentration of BiSe limits its thermoelectric performance. In this paper, Ag and Na were doped in polycrystalline BiSe to tune its thermoelectric transport properties. A series of Ag-doped and (Ag, Na) co-doped samples were synthesized via solid-phase sintering method and spark plasma sintering (SPS). It is found that Ag doping can effectively reduce the lattice thermal conductivity of BiSe, thereby reducing the total thermal conductivity, which increases the ZT value of Bi 0.97 Ag 0.03 Se from 0.24 to 0.28. Along with the co-doping of 1% Na, the carrier concentration of the (Ag, Na) co-doped sample effectively reduces from 32 × 10 19 cm −3 to 6 × 10 19 cm −3 , while the mobility greatly increases, so that the electrical conductivities are maintained in a high range, and the Seebeck coefficients are slightly increased. A maximum ZT value of 0.31 at 523 K is achieved in Bi 0.96 Ag 0.03 Na 0.01 Se along the SPS pressing direction as a result of the higher power factor and lower total thermal conductivity, which is about 30% higher than that of undoped BiSe. • (Ag, Na) co-doping optimizes thermal and electrical transport simultaneously. • Ag dopant prefers to occupying the Bi site of Bi2Se3 quintuple layers. • A 30% promotion of ZT value for (Ag, Na) co-doped BiSe is achieved.