Thermal, electrical, and structural behavior of silver chalcogenide composites

In this thesis and the contained publications, it is demonstrated that it is not only possible to improve the dimensionless figure of merit (ZT) of silver chalcogenide composites, but it is also possible to move the maximum ZT value into a more favorable temperature range for power production. It is shown that by introducing disorder, stress, and phase competition into a system, a reduction in the material's thermal conductivity can be realized. The binaries Ag2Te and Ag2Se are re-examined in detail before moving on to examine Ag2Te1-xSe x composites. The maximum ZT (ZT = 0.92) of Ag2Te0.5 Se0.5 is measured at T= 500 K, which is a more favorable temperature range for power production. Lastly, the high performing thermoelectric material Cu0.2Ag2.8SbSeTe2 is presented, which produced a ZT = 1.75 and ZT = 1.5 at T= 680 K from its respective slow-cooled and quenched samples. These results suggest that the formation of composites is a viable way to develop a phonon-glass-electron-crystal (PGEC).