Spark plasma sintered Bi-Sb-Te alloys derived from ingot scrap: Maximizing thermoelectric performance by tailoring their composition and optimizing sintering time.

Bi 2 Te 3 -based materials have been widely used in thermoelectric conversion technologies. Thermoelectric modules are fabricated from Bi 2 Te 3 -based ingots, but utilization of recycled scraps produced during the machining of thermoelectric elements has attracted attention because of limited material resources. In this work, we proposed a strategy for reusing ingot scraps to produce practical high-performance thermoelectric materials via a spark plasma sintering process by adjusting the composition of the scraps. It was found that the SPS process with a transient liquid phase resulting from excess added Te enhanced the thermoelectric performance, and a appropriately long soaking time was needed for SPS to maximize this enhancement. A longer sintering time helped improve the electrical transport properties, while simultaneously reducing the lattice thermal conductivity. Eventually, the highest ZT value of 1.33 and maximum conversion efficiency of 4.2% were obtained in the sample sintered for 15 min. This work provides an effective strategy for recycling industrial scraps of Bi 2 Te 3 -based thermoelectric materials and demonstrates the importance of soaking time optimization when spark plasma sintering is used for re-processing. Liquid Te-assisted sintering effectively enhances the thermoelectric performance of Bi-Sb-Te materials based on the recycled commercial ingot scraps. The enhancement can be further maximized by appropriately prolonging the sintering time which leads to large grains and abundant dislocations. [Display omitted] • High TE performance Bi-Sb-Te materials can be obtained by reusing the ingot scraps via liquid-assisted sintering. • The enhancement of TE performance can be maximized by appropriately prolonging the sintering time. • The present long time sintering can boost the ZT value and conversion efficiency up to 1.33 and 4.2%, respectively. [ABSTRACT FROM AUTHOR]