Study of thermal stability of n-type skutterudites Sr0.07Ba0.07Yb0.07Co4Sb12 by differential thermal analysis and Knudsen effusion method

With a high figure of merit, ZT, described in detail in the introduction, multi-filled CoSb3 skutterudites attract attention for their use as thermoelectric materials. In this work, the thermal and phase stability of n-type skutterudites, Sr0.07Ba0.07Yb0.07Co4Sb12, prepared by ball milling, hot pressing and high-pressure torsion or by combinations thereof, with ZT values of about 1.4, have been studied via differential thermal analysis and Knudsen effusion method. The results from evaporation of antimony, strontium, barium and ytterbium as the volatile elements and those from phase transformation measurements 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 thermoelectrics is evaluated. Almost no strontium, barium and ytterbium evaporation and only a slight evaporation of antimony demonstrate a long-term operation stability of the bulk and nano-structured thermoelectrics investigated.