Self-propagating high-temperature synthesis for compound thermoelectrics and new criterion for combustion processing

Abstract

The existing methods of synthesis of thermoelectric (TE) materials remain constrained to multi-step processes that are time and energy intensive. Here we demonstrate that essentially all compound thermoelectrics can be synthesized in a single-phase form at a minimal cost and on the timescale of seconds using a combustion process called self-propagating high-temperature synthesis. We illustrate this method on Cu2Se and summarize key reaction parameters for other materials. We propose a new empirically based criterion for sustainability of the combustion reaction, where the adiabatic temperature that represents the maximum temperature to which the reacting compact is raised as the combustion wave passes through, must be high enough to melt the lower melting point component. Our work opens a new avenue for ultra-fast, low-cost, large-scale production of TE materials, and provides new insights into combustion process, which greatly broaden the scope of materials that can be successfully synthesized by this technique.

Panoscopic approach for high-performance Te-doped skutterudite

“…However, the intensity of the characteristic diffraction peak of CoSb significantly decreases after the sample is held at this temperature for 6 min (sample #7). This result indicates that CoSb begins to convert to CoSb 3 and that the reaction in equation (2) becomes the overall ratedetermining event. In summary, the key factor that initiates the formation and conversion of the CoSb phase is the sintering temperature with the holding time for the diffusion process (supply of Sb) to occur.…”

“…[13][14][15][16][17] Those phonons are primarily scattered by features in the structure (dopant, nanostructures and so on) that are comparable in size to the MFP of the phonons. For example, the high-frequency (short-wavelength) phonons tend to be scattered more effectively by atomic-scale point defects, that is, doping foreign species at the sites of Co 18,19 and Sb 7,11,20,21 or introducing filler atoms [22][23][24] into the structural voids (cages) of CoSb 3 . The medium-frequency phonons with medium MFP of several to hundreds of nanometers are significantly scattered by nanoprecipitates or other nanoscale heterogeneities.…”

“…The efficiency of thermoelectric materials is governed by the dimensionless figure of merit ZT = α 2 σT/κ, where α, σ, T and κ are the Seebeck coefficient, electrical conductivity, absolute temperature and thermal conductivity, respectively. Many studies have been conducted in the past decades [1][2][3][4][5] to enhance the thermoelectric properties with a focus on improving the power factor and decreasing the thermal conductivity. Because of the high electrical transport performance 6,7 and relatively good mechanical properties, 8 skutterudites are considered notably promising for commercial power generation thermoelectric applications 9,10 in the temperature range of 500-900 K. 6,7,11,12 However, the disadvantage of skutterudites is their notably high lattice thermal conductivity of 410 W m − 1 K − 1 .…”

On the tuning of electrical and thermal transport in thermoelectrics: an integrated theory–experiment perspective

“…193 The culprit is the critical conditions necessary to follow when synthesising TE bulk materials. New techniques for rapid synthesis, such as the self-propagating high-temperature synthesis, 194 could be a solution to high-throughput experimentation with TE materials.…”

Microstructure and Thermoelectric Properties of Bulk Cobalt Antimonide (CoSb3) Skutterudites Obtained by Pulse Plasma Sintering

“…[12][13][14] Recently, utilization of selfpropagating high-temperature synthesis (SHS) as a very fast and effective method for skutterudite synthesis has been presented. 15 16 In the present work, the use of the pulse plasma sintering (PPS) technique for consolidation of thermoelectric materials is reported. This method is a type of pulsed current method used in powder metallurgy, of which the most prominent representative is SPS.…”