Suppressing the thermal conductivity to enhance the thermoelectric performance of SnSe2 using the high-energy ball milling in a pressurised N2 atmosphere

Abstract

Two-dimensional (2D) layered dichalcogenides possess excellent thermoelectric (TE) properties. Among them, tin diselenide (SnSe2) exhibits n-type semiconducting properties with attractive TE performance near room temperature (RT). However, its high thermal conductivity and relatively low electrical conductivity have limited its TE performance for practical applications. In this study, we significantly suppressed the thermal conductivity and enhanced the TE performance of 2D layered SnSe2 polycrystalline structures by reducing the particle size to the nano-scale using the high-energy ball milling (BM) technique in a pressurised N2 atmosphere. The particle size was reduced from ∼2 μm to 100 nm after 15 h of BM. TE results of a highly pressed compact leg made from the TE-optimised BM sample (e.g. 7 h) showed that at RT, the electrical conductivity increased by a factor of 9, whereas the Seebeck coefficient was reduced by only 40%. Consequently, the power factor increased from 12 to 42 μW/m·K2. In addition, the thermal conductivity decreased from 5.72 to 0.40 W/m·K, resulting in a significant increase in the figure of merit by a factor of 40 times higher than that of the non-BM SnSe2 leg. This study also demonstrated power generation using single-leg modules made from these structures at ΔT values above and below RT. The TE power generation of the BM module was found to be much higher than that of the non-BM module, particularly below RT. The 7-h BM module generated 2600 nW at ΔT = 45 K above RT, but when the same ΔT was applied below RT, the generated power reached 8000 nW. This enhancement in power generation below RT is remarkable, suggesting that the BM SnSe2 compact may be useful for generating measurable TE power in cold environments.

Keywords

• SnSe2
• High-energy ball milling
• Thermoelectric
• TE power generation
• TE module