Arige HODROJ PhD defense
Metallothermic synthesis and protection against oxidation of thermoelectric skutterudites
Jueves 6 noviembre, 14:30Pasado
Solid State Chemistry and Materials (CSM) team
Abstract
Magnesiothermic synthesis has proven to be an effective route for producing thermo-electric skutterudites at lower temperatures and in shorter times, while yielding submicron grains.
In this work, the method was scaled up from 1 gram to about ten grams for the synthesis of the n-type In0.2Co4Sb12. The influence of the reaction parameters, as well as the underlying reaction mechanisms, were studied in detail to optimize purity, and homogeneity. Optimized 10 g batches exhibited high reproducibility and competitive thermoelectric performance, reaching a figure of merit up to ZT ≈ 1.1, comparable with the best values reported in the literature. In parallel, adaptation of this route to the p-type Ce0.75Fe3CoSb12 proved promising, as the phase could be obtained on several syntheses but with limited reproducibility, highlighting both the feasibility and the challenges of achieving consistent yields by magnesiothermic synthesis. Beyond synthesis, the intrinsic susceptibility of these materials to oxidation at operating temperatures was addressed. Since no detailed reports existed for In-filled skutterudites, the oxidation behavior of the n-type was systematically investigated, and magnesioreduced samples displayed enhanced stability compared to conventionally synthesized ones, a behavior attributed to their refined microstructure with submicron grains, sharp grain boundaries, and the absence of secondary phases, as evidenced by SEM, EBSD, and TEM analyses. Protective strategies were investigated and tested under isothermal and cycling conditions, and their effectiveness in preventing oxidation was evaluated.
Jury
- Nicole Fréty, Professeure, ICGM, Montpellier / Reporter
- Emmanuel Guilmeau, Directeur de recherche, CNRS, CRISMAT, Caen / Reporter
- Nicolas Emery, Chargé de recherche, CNRS, ICMPE, Thiais / Examiner
- Philippe Castany, Professeur, INSA, ISCR, Rennes / Examiner
- Mathieu Pasturel, Directeur de recherche, CNRS, ISCR, Rennes / PhD Supervisor
- Valérie Bouquet, Maitre de conférences, ISCR, Rennes / PhD Co-Supervisor
Contacts
Mathieu Pasturel, mathieu.pasturel@univ-rennes.fr
Valerie Bouquet, valerie.bouquet@univ-rennes.fr
Arige Hodroj, arige.hodroj@univ-rennes.fr
