Enhanced Thermoelectric Figure-of-Merit in Nanostructured p-type Silicon Germanium Bulk Alloys

Abstract

A dimensionless thermoelectric figure-of-merit (ZT) of 0.95 in p-type nanostructured bulk silicon germanium (SiGe) alloys is achieved, which is about 90% higher than what is currently used in space flight missions, and 50% higher than the reported record in p-type SiGe alloys. These nanostructured bulk materials were made by using a direct current-induced hot press of mechanically alloyed nanopowders that were initially synthesized by ball milling of commercial grade Si and Ge chunks with boron powder. The enhancement of ZT is due to a large reduction of thermal conductivity caused by the increased phonon scattering at the grain boundaries of the nanostructures combined with an increased power factor at high temperatures.

Assessing the Thermoelectric Properties of Sintered Compounds via High-ThroughputAb-InitioCalculations

“…To tackle the problem, several nanostructured materials have been proposed since the late 1990s [4]. Among them, the sintered powder nanocomposites stand out as cost-effective solutions with improved thermoelectric efficiency [5][6][7][8][9]. In these materials, the presence of grain boundaries alters the electron-and phonon-scattering mechanisms.…”

Silicide Nanopowders as Low-Cost and High-Performance Thermoelectric Materials

“…They have achieved a high ZT of 1.4 at 100°C. The same groups also reported a similar ball milling-hot pressing approach for other materials including Si-Ge alloy 16 and n-type Si, 21 among many others. Another recently developed approach is melt-spinning ribbons of the appropriate alloy, hand-grinding them, and compacting them by spark plasma sintering (SPS).…”

“…The thermoelectric properties of various nanocomposite materials have been reported. [16][17][18][19][20] Among numerous reports, the most popular methods for producing thermoelectric nanopowders are based on top-down approaches. For example, Poudel et al 17 reported the fabrication of nanocomposite p-type Bi 0.5 Sb 1.5 Te 3 by ball milling the bulk alloys for extended hours to nanometer dimensions in inert environments and hot-pressing these nanopowders to produce the sintered compacts.…”

“…17), Si (Ref. 21), and Si-Ge alloy, 16 etc. Therefore, it can be an attractive technique for producing large-scale quantity of Mg 2 Si.…”

Constitutive equations for heat conduction in nanosystems and nonequilibrium processes: an overview

“…Nanomaterials provide an interesting avenue to obtain more performing thermoelectric devices, for example, making nanocomposites, adding nanoparticles to a bulk material, or using one-dimensional nanostructures [66,67].…”