Enhanced thermoelectric and mechanical properties of Na-doped polycrystalline SnSe thermoelectric materials via CNTs dispersion

SnSe-based thermoelectric materials have captured much attention since single-crystal SnSe exhibited record high ZT. However, the practical application is limited due to the poor mechanical properties and harsh production conditions of single crystals. Herein, we achieve high thermoelectric performances and enhanced mechanical properties in the Na-doped polycrystalline SnSe through implanting carbon nanotubes (CNTs). The CNTs are truncated and uniformly dispersed within the Na-doped SnSe matrix via a combination of cryogenic grinding and spark plasma sintering technique. It is found that Na-doped polycrystalline SnSe/CNTs composites maintain high carrier concentrations of approximately 4 × 10¹⁹ cm⁻³ at room temperature, resulting in great power factors. The dispersion of CNTs reduces the thermal conductivity without significant deterioration on the electrical conductivity. A maximum ZT of ∼0.96 at 773 K is achieved via adding merely 0.25 vol% CNTs. More fundamentally, the Na-doped polycrystalline SnSe samples incorporated with CNTs show superior mechanical properties, which are favorable for device fabrication and practical applications.