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PhD student M/F . "Optimization of thermoelectric and optoelectronic properties of 2D chalcogenide materials by texturing"

This offer is available in the following languages:
Français - Anglais

Date Limite Candidature : mardi 11 octobre 2022

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General information

Reference : UMR6502-STEJOB-003
Workplace : NANTES
Date of publication : Tuesday, September 20, 2022
Scientific Responsible name : Stephane Jobic / Laurent Cario / David Berthebaud
Type of Contract : PhD Student contract / Thesis offer
Contract Period : 36 months
Start date of the thesis : 1 December 2022
Proportion of work : Full time
Remuneration : 2 135,00 € gross monthly

Description of the thesis topic

Solid chalcogenide-based compounds have often the propensity to crystallize in 2D structures. Hence, BiOCuQ (Q = S, Se and Te) or misfit sulfur compounds such as (LaS)1.14(TS2) (T = Cr , Nb, ...) show a wide range of properties and functionalities (thermoelectricity, optoelectronics, superconductivity…). These properties can be modulated by doping, but it is also possible to take advantage of their anisotropies to optimize their physical characteristics by improving the mobility of the charge carriers in the plane of the conductive layers by adjusting their texturing. The texturing techniques commonly used in materials chemistry are uniaxial pressure sintering of powder consisting of particles with anisotropic morphology or the hot forging process. These processes, which are quite simple to implement, only allow a weak control of the orientation of the particles. Here, the recruited PhD student will use innovative techniques for texturing materials, including the slip casting texturing process of a suspension under a magnetic field. The application of a magnetic field during casting makes it possible to force the orientation of the particles in suspension along their axis of easy magnetization and therefore to provide control over the final texture of the material. The preparation of stable suspensions whose individual particles couple optimally with the magnetic field, is a key aspect for the successful use of this technique. The optimization of this process will be done in collaboration with Prof. Tohru S. Suzuki of NIMS (Japan), a specialist in this type of process and involved in the LINK laboratory, which has a fleet of appropriate equipment (modular, orientable and rotating superconducting magnets, which in particular allow the synthesis of large samples). The IMN has a long experience in the chemistry of chalcogenides as well as in the characterization of their optoelectronic properties. The doctoral student recruited and assigned to the IMN will therefore have access to all the techniques necessary to synthesize chalcogenide materials in 2D layers (sulfur bench, mechano-synthesis, solvothermal synthesis, sealed tube, etc.) in the form of particles of the appropriate size to obtain a sufficiently stable dispersion, necessary for the process of alignment under field. At LINK a special focus will be given to the thermoelectric properties of the textured materials.
The recruited student will have to visit the LINK laboratory (Saint-Gobain/CNRS/NIMS international research laboratory) to shape his (her) samples and determine the thermoelectric properties of textured materials.

Work Context

The PhD grant is associated to an INTERNATIONAL THESIS funded by CNRS in the framework of a collaboration between IMN, Nantes (UMR 6502, https://www.cnrs-imn.fr/) and LINK, Tsukuba (IRL 3629, https://link.cnrs.fr/).
The project will take place within the chalcogenide axis at IMN in collaboration with the International Research Laboratory LINK (Laboratory for Innovative Key Materials and Structure) located at the National Institute for Materials Science, Tsukuba, Japan. This joint laboratory created in 2014 aims at representing an innovative collaboration model between two academic, NIMS and CNRS, and one industrial partners, Saint-Gobain.
Within this international project, the student will be trained at IMN under the supervision of Stephane Jobic and Laurent Cario on the synthesis and characterization of layered chalcogenides. At LINK, the student will be supervised by David Berthebaud and will work in close collaboration with Pr. Tohru Suzuki to be trained on texturation process under magnetic field. He/She will also have access to state-of-the-art facility at NIMS to characterize his/her materials properties (thermoelectric, optoelectronics …). Mobility (6-12 months) between France and Japan is expected for the completion of this project.

The doctoral school is the ED3M at Nantes Université, France

Constraints and risks

use of X-ray diffraction for structural characterization of synthesized materials
synthesis of nanostructured materials
orientation of particles in suspension under magnetic field

Additional Information

The candidate will have a strong scientific curiosity and the will to develop a strong expertise in the fields of solid-state chemistry. With a M2 and/or engineering school degree in materials science, he/she should have a solid and varied background in both synthesis (solid state reactions, soft chemistry) and characterization (X-ray diffraction, thermoelectric measurements, magnetism, optical properties) of materials. He/she will participate in the activities of the chalcogenide axis at IMN and the LINK in Japan and will be required to present his/her work at national or international conferences. A good level of English is required. The candidate should send a detailed CV, and a letter of motivation.

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