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

Compounds of CuxBi2Te3 (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 Cu0.07Bi2Te3 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. Cu0.07Bi2Te3 had high electrical conductivity of 681 S cm(-1) and Seebeck coefficient of -236 mu V 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.