Studies on the Bi[subscript 2]Te[subscript 3]–Bi[subscript 2]Se[subscript 3]–Bi[subscript 2]S[subscript 3] system for mid-temperature thermoelectric energy conversion

Abstract

Bismuth telluride (Bi[subscript 2]Te[subscript 3]) and its alloys have been widely investigated as thermoelectric materials for cooling applications at around room temperature. We report a systematic study on many compounds in the Bi[subscript 2]Te[subscript 3]–Bi[subscript 2]Se[subscript 3]–Bi[subscript 2]S[subscript 3] system. All the samples were fabricated by high energy ball milling followed by hot pressing. Among the investigated compounds, Bi[subscript 2]Te[subscript 2]S[subscript 1] shows a peak ZT ~0.8 at 300 °C and Bi[subscript 2]Se[subscript 1]S[subscript 2] ~0.8 at 500 °C. The results show that these compounds can be used for mid-temperature power generation applications. The leg efficiency of thermoelectric conversion for segmented elements based on these n-type materials could potentially reach 12.5% with a cold side at 25 °C and a hot side at 500 °C if appropriate p-type legs are paired, which could compete well with the state-of-the-art n-type materials within the same temperature range, including lead tellurides, lead selenides, lead sulfides, filled-skutterudites, and half Heuslers.