Enhanced thermoelectric performance of BiSe by Sn doping and ball milling

Abstract BiSe has emerged as a promising Te-free high-performance thermoelectric (TE) material base owing to its ultra-low lattice thermal conductivity caused by the Bi bilayers in its lattice. Herein, the TE properties of BiSe were modified by Sn doping and ball milling to improve its performance. The ball milling process reduced the grain size of the samples and affected their anisotropy during the pressing process, leading to the random arrangement of the (00 l ) plane, which improved the electrical conductivity of the samples in the direction parallel to the spark plasma sintering direction and increased the Seebeck coefficient. The increased defects and smaller grain size of the samples due to Sn doping and ball milling enhanced the scattering of phonon transport, thereby decreasing the lattice thermal conductivity. The improvement in the ZT of the samples was realized through the improvement in their thermal and electrical transport. The Spark plasma-sintered bulk of the ball-milled Bi0.9Sn0.1Se sample exhibited a high-power factor of 8.4 μW · cm−1 · K−2 at 473 K and an ultra-low lattice thermal conductivity of 0.43 W · m−1 · K−1 at 673 K along with the maximum ZT value of 0.32 at 473 K, which is 31.6% higher than that of the pristine BiSe sample.