A strategy to optimize the thermoelectric performance in a spark plasma sintering process

Abstract

Spark plasma sintering (SPS) is currently widely applied to existing alloys as a means of further enhancing the alloys’ figure of merit. However, the determination of the optimal sintering condition is challenging in the SPS process. This report demonstrates a systematic way to independently optimize the Seebeck coefficient S and the ratio of electrical to thermal conductivity (σ/κ) and thus achieve the maximum figure of merit zT = S2(σ/κ)T. Sb2−xInxTe3 (x = 0–0.2) were chosen as examples to validate the method. Although high sintering temperature and pressure are helpful in enhancing the compactness and electrical conductivity of pressed samples, the resultant deteriorated Seebeck coefficient and increasing thermal conductivity eventually offset the benefit. We found that the optimal sintering temperature coincides with temperatures at which the maximum Seebeck coefficient begins to degrade, whereas the optimal sintering pressure coincided with the pressure at which the σ/κ ratio reaches a maximum. Based on this principle, the optimized sintering conditions were determined, and the zT of Sb1.9In0.1Te3 is raised to 0.92 at 600 K, showing an approximately 84% enhancement. This work develops a facile strategy for selecting the optimal SPS sintering condition to further enhance the zT of bulk specimens.

Fabrication of Skutterudite-Based Tubular Thermoelectric Generator

“…Co-sintering can be detrimental to the thermoelectric properties, since the optimum sintering temperature and pressure vary for n-and p-type TE materials due to the difference in composition. For example, Chiu et al reported that only a temperature difference of 50 K from the optimum sintering condition can result in a drop of the overall thermoelectric properties, especially zT by 75% of the optimum value [32]. Generally, in the case of skutterudite, the difference of the sintering temperature between the p-type and the n-type is about 100 K [14], which can significantly affect the property.…”

Thickness Effects for Thermoelectric Property of Antimony Telluride Nanoplatelets via Solvothermal Method

“…The dominant effect of lowering thermal conductivity in nanostructuring materials is tuning the size and porosity of crystal grains78. The morphology and dimension of crystals play important roles in regulating transport of carriers and phonons910.…”

“…The effective mean free path for grain boundary scattering is closely related to the average grain size. Tailoring the grain size to optimize the transport of phonon is a crucial strategy for high thermoelectric materials1213.…”

Anomalous thermoelectricity in strained Bi2Te3 films

“…Actually, they are also famous thermoelectric materials with high thermoelectric coefficient near room temperature (RT) for applications in waste-heat recovery, refrigeration or portable power generation, since they possess notable properties such as a prominent Seebeck effect, low thermal conductivity and high value of the carrier concentration in RT45678. The thermoelectric performance of materials is evaluated by figure of merit ZT  = ( S 2 σ / k ) T , where S is the Seebeck coefficient, σ is the electrical conductivity, k is the thermal conductivity, and T is the absolute temperature891011121314. In the past decades, many kinds of methods have been developed to improve the ZT value through modulating the parameters S , σ and k in order to improve the conversion efficiency of thermoelectric devices101315.…”

“…The thermoelectric performance of materials is evaluated by figure of merit ZT  = ( S 2 σ / k ) T , where S is the Seebeck coefficient, σ is the electrical conductivity, k is the thermal conductivity, and T is the absolute temperature891011121314. In the past decades, many kinds of methods have been developed to improve the ZT value through modulating the parameters S , σ and k in order to improve the conversion efficiency of thermoelectric devices101315. For example, donor or acceptor impurities and other elements are doping into the alloys in order to optimize the charge carrier concentration, but they usually increase the k at the same time51617.…”