Study of thermodynamic behavior and thermal stability of advanced thermoelectric materials


Zelenka František


Doped skutterudites and Half-Heuslers alloys attract attention for their use as thermoelectric
materials, possessing a high figure of merit, ZT. In this work the thermal and phase stability of
various thermoelectric materials, prepared by ball milling, hot pressing and high pressure torsion
or by their combinations, with high ZT values, have been studied via thermal analysis and the
Knudsen effusion condensation method. The results from evaporation of volatile elements are
presented. The information, supported by microstructure investigation and measurement of diffusion
profiles, is summarized and the long-term operation stability of the studied bulk and
nano-structured thermoelectric were evaluated. Long term stability evaluation is supported by
in-situ electron microscopy at high temperatures. This approach allow us to evaluate sublimation
processes in the thermoelectric materials at high temperatures.