In-situ elevated-temperature TEM study of (AgSbTe2)15(GeTe)85

(AgSbTe₂)₁₅(GeTe)₈₅ (TAGS-85) is a p-type semiconductor characterized by a maximum dimensionless thermoelectric figure of merit of 1.4–1.7 at elevated temperature. In this study, the microstructure of as-solidified TAGS-85 at room temperature and elevated temperature (160 °C) was investigated using TEM. At room temperature, pervasive twinning was observed throughout the specimen. Upon heating to above 120 °C, some of the twins dissolved and new point defects began to nucleate. The mechanisms responsible for formation of high temperature defects are discussed.