One-Step Hydrothermal Synthesis of Amorphous Carbon-Coated PbTe Nanowires for Thermoelectric Applications

Abstract

Thennoelectric materials have potential applications in power generation, cooling, and thennal sensing. Lead tel1uride (PbTe) has been identified as an ideal material for high-perfonnance thennoelectric devices because of its narrow band gap (0.32 eV at 300 K) and large Bohr radius (~46 nm) possessing strong quantum confinement effect within a large range of size. Recently, it has been reported that PbTe nanostructures have largely improved energy conversion efficiency compared with their bulk counterparts. 1n particular, one-dimensional (lD) PbTe nanostructures have attracted considerable interest for their potential applications in high-perfonnance thennoelectric device construction. However, the adsorption of unwanted species (such as water and oxygen) on the surface and unnecessary charge injection into PbTe nanowires could negatively affect device characteristics or stability. One possible solution of these problems could be to fabricate the PbTe nanowires with insulating sheaths. 1n this work, carbon-coated PbTe nanowires were successfully synthesized through a facile one-step hydrothennal process using ascorbic acid as a reducing agent and carbonization source. The average diameter of PbTe core nanowires and thickness of amorphous carbon sheaths are about 20 and 10 nm, respectively. Sequential mechanism for the phase fonnation, shape evolution, and carbon sheath fonnation was also investigated from the experiment results for various reaction times in detail. During this process, carbon-coated Te nanowires were fonned and then reacted with Pb2+ ions in the solution, resulting in the fonnation of carbon-coated PbTe nanowlres. The phase of obtained products was characterized by X-ray diffraction (XRD). Field emission scanning electron microscopy (FE-SEM), and transmission electron microscopy (TEM) were exploited to observe the morphology and size of the products. 1n order to analyze the sheaths on the surface of PbTe nanowires, the room temperature Raman spectra were also recorded.