Formation of Cu nanoparticles in layered Bi2Te3 and their effect on ZT enhancement

Abstract

Compounds of Cu_xBi₂Te₃ (0 ≤ x ≤ 0.1) were studied to measure the effect of Cu intercalation on their thermoelectric properties. HR-TEM images of freshly fractured surfaces of Cu_0.07Bi₂Te₃ showed that Cu nanoparticles formed in the van der Waals gaps between Te layers in Bi₂Te₃. Such nanoparticles acted as electron donors, changing the native p-type character of Bi₂Te₃ to n-type. They also acted as phonon scatters, reducing thermal conductivity. Cu_0.07Bi₂Te₃ had high electrical conductivity of 681 S cm⁻¹ and Seebeck coefficient of −236 μV K⁻¹ with low thermal conductivity of 1.0 W m⁻¹ K⁻¹, thus enhancing the figure of merit, ZT, to 1.15 at approximately 300 K. The intercalation of metal nanoparticles between Te layers in Bi₂Te₃ is a promising strategy for the preparation of highly efficient n-type thermoelectric materials.