Domaine, spécialité : Chimie des matériaux
Mots-Clés : Conductivité thermique
Unité d’accueil : LLB / NFMQ
Résumé
L’objectif de ce stage de M2 sera d’étudier expérimentalement la conductivité thermique d’un grenat de terres rares présentant un désordre élevé à l’aide de l’approche à haute entropie.
Sujet détaillé
Understanding the parameters which determine the magnitude of thermal conductivity (Κ) in solids is of both fundamental and technological interests. Κ is sensitive to all quasiparticles carrying energy, whether charged or neutral. Foremost among these are phonons, the collective vibrations of atoms in crystals. In terms of applications, thermal properties of solids are at the heart of major social and environmental issues. The need, for instance, for highly efficient thermoelectric and thermal barrier devices to save energy has driven the quest for low thermal conductors. Over time, a range of strategies has thus been suggested to hinder phonon velocities and/or mean free paths: use of weak interatomic bonds, strong anharmonicity, nanoscale designs, or complex or disordered unit cells. Another promising concept to further impair the phonon mean-free path is based on magneto-elastic coupling.
This concept has emerged from the observation of a spin-phonon coupling in some rare-earth perovskites, pyrochlores or garnets. The magnetic excitations involved in the magneto-elastic coupling at play in those compounds are low energy crystal field excitations (CEF). Those are local electronic excitations, thus they do not contribute to κ ; they can significantly reduce the phonon lifetime, however, through new phonon scattering mechanisms.
The aim of this M2 internship will be therefore to investigate experimentally the thermal conductivity of a rare-earth garnet with high disorder using the high-entropy approach.
Lieu du stage
CEA Saclay, (91) Essonne, France
Conditions de stage
- Durée du stage : 6 mois
- Niveau d’étude requis : Bac+5
- Formation : Master 2
- Poursuite possible en thèse : Oui
- Date limite de candidature : 2 mars 2026
Compétences requises
Langue : Anglais
Méthodes, techniques :
During this internship you will:
- Synthesize a high-entropy crystalline rare-earth garnet single crystal, with high entropy on the A-site (rare-earth site) of the garnet crystal structure, in collaboration with ICMMO, a solid-state chemistry laboratory at Université Paris-Saclay,
- Perform comprehensive thermal conductivity and specific heat measurements down to sub-kelvin temperature on state-of-the art experimental setups, at ICMMO or at ESPCI (Paris),
- If time allows, carry out neutron scattering experiments in a large-scale facility such as ILL, to study CEF dynamics
Liens utiles
- Page Internet du responsable de stage : Francoise Damay
- Page internet du laboratoire : LLB/NFMQ