A cubic room temperature polymorph of thermoelectric TAGS-85+

Anil Kumar, Paul A. Vermeulen, Bart J. Kooi, Jiancun Rao, Stefan Schwarzmueller, Oliver Oeckler, Graeme R. Blake*

*Bijbehorende auteur voor dit werk

OnderzoeksoutputAcademicpeer review

1 Citaat (Scopus)
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Samenvatting

The alloy (GeTe)(85)(AgSbTe2)(15), commonly known as TAGS-85, is one of the best performing p-type thermoelectric materials in the temperature range 200-500 degrees C. In all reports thus far, TAGS-85 adopts a rhombohedral crystal structure at room temperature and undergoes a reversible transition to a cubic phase in the middle of the operating temperature range. Here, we report on a novel, metrically cubic polymorph of TAGS-85 that can be obtained at room temperature using a particular cooling protocol during initial synthesis. This polymorph transforms irreversibly on initial heating to a 21-layer trigonal structure containing ordered cation vacancy layers, driven by the spontaneous precipitation of argyrodite-type Ag8GeTe6. We show that the precipitation of Ag8GeTe6 is detrimental to the thermoelectric performance of TAGS-85 due to an increase in the vacancy concentration, which makes the samples more metallic in character and significantly reduces the Seebeck coefficient. The precipitation of Ag8GeTe6 can be suppressed by careful control of the synthesis conditions.

Originele taal-2English
Pagina's (van-tot)42322-42328
Aantal pagina's7
TijdschriftRSC Advances
Volume8
Nummer van het tijdschrift74
DOI's
StatusPublished - 2018

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