Interface Driven Energy Filtering of Thermoelectric Power in Spark Plasma Sintered Bi₂Te_2.7Se_0.3 Nanoplatelet Composites

Abstract

Control of competing parameters such as thermoelectric (TE) power and electrical and thermal conductivities is essential for the high performance of thermoelectric materials. Bulk-nanocomposite materials have shown a promising improvement in the TE performance due to poor thermal conductivity and charge carrier filtering by interfaces and grain boundaries. Consequently, it has become pressingly important to understand the formation mechanisms, stability of interfaces and grain boundaries along with subsequent effects on the physical properties. We report here the effects of the thermodynamic environment during spark plasma sintering (SPS) on the TE performance of bulk-nanocomposites of chemically synthesized Bi(2)Te(2.7)Se(0.3) nanoplatelets. Four pellets of nanoplatelets powder synthesized in the same batch have been made by SPS at different temperatures of 230, 250, 280, and 350 °C. The X-ray diffraction, transmission electron microscopy, thermoelectric, and thermal transport measurements illustrate that the pellet sintered at 250 °C shows a minimum grain growth and an optimal number of interfaces for efficient TE figure of merit, ZT∼0.55. For the high temperature (350 °C) pelletized nanoplatelet composites, the concurrent rise in electrical and thermal conductivities with a deleterious decrease in thermoelectric power have been observed, which results because of the grain growth and rearrangements of the interfaces and grain boundaries. Cross section electron microscopy investigations indeed show significant grain growth. Our study highlights an optimized temperature range for the pelletization of the nanoplatelet composites for TE applications. The results provide a subtle understanding of the grain growth mechanism and the filtering of low energy electrons and phonons with thermoelectric interfaces.

Enhancing thermoelectric performance of Bi2Te3-based nanostructures through rational structure design

“…12 Especially, rhombohedral structured Bi 2 Te 3 nanoplates, as twodimensional nanostructures, [13][14][15] exhibit strengthened phonon scattering due to the dense grain boundaries after sintered into pellets. 16 To further strengthen the phonon scattering, we can assemble the randomly orientated nanoplates in the form of well-aligned hierarchical nanostructures.…”

Thickness and strain effects on the thermoelectric transport in nanostructured Bi2Se3

“…1, and the references therein. Nanostructuring, alloying, and the application of strain are effective and frequently used approaches [2][3][4] to improve TE properties, because the phonon scattering is enhanced, and the thermal conductivity consequently is reduced.…”

Síntesis e investigación del mono cristal BiSBTeSe dopado con Zr obtenido mediante el método de Bridgman

“…Transport property measurements in doped Bi 2 Te 3 single crystals with Se and Fe have been studied by measuring the thermoelectric power and electrical conductivity in the temperature range 30 ºC to 200 ºC (Jariwala et al, 2015). They focused on improving the transport properties by better control of the stoichiometry through a uniform impurity distribution during the growth process.Se doped Bi 2 Te 3 single crystals have been reported to be thermoelectric materials with maximum figure of merit, ZT~1.04 at 125 ºC (Yan et al, 2010;Soni et al, 2012;Guo et al, 2014;Jariwala et al, 2015). (BiSb) 2 (TeSe) 3 belongs to the family of narrow-band semiconductors A 2 V B 3 VI (A = Bi, Sb and B = Te, Se) with the tetradymite structure (Kašparová et al, 2005;Rowe, 2005).…”