Enhanced thermoelectric properties of polycrystalline Bi2Te3 core fibers with preferentially oriented nanosheets

Bi 2 Te 3 -based materials have been reported to be one of the best room-temperature thermoelectric materials, and it is a challenge to substantially improve their thermoelectric properties. Here novel Bi 2 Te 3 core fibers with borosilicate glass cladding were fabricated utilizing a modified molten core drawing method. The Bi 2 Te 3 core of the fiber was found to consist of hexagonal polycrystalline nanosheets, and polycrystalline nanosheets had a preferential orientation; in other words, the hexagonal Bi 2 Te 3 lamellar cleavage more tended to be parallel to the symmetry axis of the fibers. Compared with a homemade 3-mm-diameter Bi 2 Te 3 rod, the polycrystalline nanosheets’ preferential orientation in the 89- μ m-diameter Bi 2 Te 3 core increased its electrical conductivity, but deduced its Seebeck coefficient. The Bi 2 Te 3 core exhibits an ultrahigh ZT of 0.73 at 300 K, which is 232% higher than that of the Bi 2 Te 3 rod. The demonstration of fibers with oriented nano-polycrystalline core and the integration with an efficient fabrication technique will pave the way for the fabrication of high-performance thermoelectric fibers.