Enhancement of the Thermoelectric Performance of 2D SnSe Nanoplates through Incorporation of Magnetic Nanoprecipitates

Abstract

Single crystals of tin selenide (SnSe), a layered material, have recently drawn massive attention in the field of thermoelectrics for its low thermal conductivity and high thermoelectric figure of merit (zT). However, nanocrystalline SnSe always remains a better choice for thermoelectric applications owing to its simple synthesis and machinability. On the other hand, enhancement of the thermoelectric performance can be achieved by the incorporation of magnetic nanoprecipitates in a thermoelectric host matrix. Herein, we have demonstrated the significant enhancement in the thermoelectric performance of the two-dimensional (2D) nanoplates of SnSe by introducing magnetic Gd dopants, which are synthesized and scaled up (∼10 g) by a low-temperature hydrothermal method. The p-type carrier concentration increases significantly upon 3 mol % Gd addition in SnSe nanoplates due to phase separation of Gd 2 Se 3 nanoprecipitates (2−5 nm) and subsequent Sn 2+ vacancy formation. Thus, the thermoelectric power factor has been markedly enhanced to 6.7 μW/(cm K 2 ) at 868 K compared to that of the pristine SnSe nanoplates. The presence of magnetic fluctuations induced by small nanoprecipitates of Gd 2 Se 3 provides additional scattering of the phonons in SnSe, which reduces the lattice thermal conductivity significantly to 0.41 W/(m K) at 868 K in Sn 0.97 Gd 0.03 Se. We have achieved a zT of ∼1 at 868 K for the spark plasma sintered (SPS) Sn 0.97 Gd 0.03 Se nanoplates along the perpendicular to the pressing direction.

Slowing down the heat in thermoelectrics

“…Two‐dimensional (2D) planar defects, including stacking faults and boundaries between grains and phases, scatter low‐frequency phonons with dislocation allays 75–78 . Three‐dimensional (3D) body defects effectively scatter phonons with ranged frequencies owing to the different sizes of nanoprecipitates, secondary phases, and porous structures 21,22,79–85 . The introduction of multiscale extrinsic defects to reduce κ lat has become a very advanced approach in the thermoelectric field 26,86–94 .…”

Ultralow Thermal Conductivity and Enhanced Figure of Merit for CuSbSe2 via Cd-Doping

“…Among all the CuSbSe 2 based system reported so far, our sample CuSb 0.98 Cd 0.02 Se 2 has the best thermoelectric performance. Meanwhile, ZT for some typical metal selenides ,− are compared (shown in Figure ). Although, as compared with some other metal selenides, the ZT values of the CuSbSe 2 based system are not very large at present; it can be expected that there is a large room to raise its ZT , considering that the pristine CuSbSe 2 has a very large Seebeck coefficient.…”

Modulation of the electronic structure and thermoelectric properties of orthorhombic and cubic SnSe by AgBiSe2 alloying

“…The sharp increase in electrical conductivity at 610 K for orthorhombic (SnSe) 0.78 (AgBiSe 2 ) 0.22 is an indication of the phase transition from lower symmetric Pnma to higher symmetric Cmcm phase. 24,45 Solid solution mixing of AgBiSe 2 with SnSe significantly increases σ due to the enhancement in the carrier concentration from 8.9 × 10 17 cm -3 for pristine SnSe to 8.2 × 10 19 cm -3 in (SnSe) 0.78 (AgBiSe 2 ) 0.22 .…”