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PhD opportunity: New functional oxides by crystallisation of amorphous precursors (M/F)

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

Date Limite Candidature : vendredi 23 avril 2021

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General information

Reference : UPR3079-MICPIT-003
Workplace : ORLEANS
Date of publication : Friday, April 02, 2021
Scientific Responsible name : Michael PITCHER
Type of Contract : PhD Student contract / Thesis offer
Contract Period : 36 months
Start date of the thesis : 1 October 2021
Proportion of work : Full time
Remuneration : 2 135,00 € gross monthly

Description of the thesis topic

The project:
This is an exploratory solid-state chemistry project which aims to discover new oxide materials using unconventional non-equilibrium synthesis methods. The project will make use of laser-assisted aerodynamic levitation melting in parallel with mechanical activation techniques as a route to metastable compounds with new compositions and crystal structures, with potential functional properties including ionic conductivity, optical transparency, luminescence or ferroic properties. The synthesis work will be partially supported by composition-prediction calculations in collaboration with the University of Liverpool (U.K.). The prepared materials will be characterized at multiple length scales and temperatures: this will include powder diffraction methods (e.g. non-ambient PXRD <2000°C using the in-house high-temperature platform; and ab-initio structure solution from synchrotron X-ray diffraction and neutron diffraction data), high-resolution transmission electron microscopy using state-of-the-art instrumentation (available for diffraction, STEM-HAADF, EELS and high-temperature in-situ measurements), and high-temperature high-field solid-state NMR. Property measurements (e.g. impedance spectroscopy) will be conducted both in-house and with established external collaborators including international partners.

The context:
At CEMHTI (CNRS UPR3079), we are pioneering the use of containerless aerodynamic levitation (ADL) apparatus with laser heating to synthesise precursor glasses and melts of diverse compositions, and crystallising these at relatively low temperatures to produce highly dense oxide ceramics with new compositions, crystal structures and/or microstructures that host desirable physical properties for optical and ionic transport applications (http://www.cemhti.cnrs-orleans.fr/instruments/levitation.aspx). Using this method, we have recently isolated new melilite-type oxide ion conductors (doi.org/10.1021/acs.chemmater.0c03441) and new luminescent YAG materials with extraordinary non-stoichiometric compositions (European patent application N° 21305159.2; manuscript in preparation). In parallel with ADL, this project will expand the glass/melt-crystallisation synthesis concept by using mechanical activation methods (e.g. high energy ball milling) to produce amorphous precursors at low temperatures, allowing access to a wider range of compositions. This PhD position is funded by the ANR project “CAPRE”.

The candidate:
We would welcome applicants with a good undergraduate degree in the physical sciences (e.g. chemistry, materials science, physics) who have completed a masters project related to solid state science. The successful candidate will join a team of PhD students and engineers with a range of international backgrounds, and may have opportunities to travel to access specific expertise and facilities. The University of Orléans offers teaching experience. Funding for 3 years is available. A starting date of October – November 2021 is envisaged.

Selected recent publications from the team:
“Highly non stoichiometric garnet ceramics for optical function”, European Patent Application N° 21305159.2 (2021)
“La2Ga3O7.5: A metastable ternary melilite with a super-excess of interstitial oxide ions synthesized by direct crystallization of the melt”, Chemistry of Materials (2020) doi.org/10.1021/acs.chemmater.0c03441
“Cooperative mechanisms of oxygen vacancy stabilization and migration in the isolated tetrahedral anion Scheelite structure”, Nature Communications (2018) doi.org/10.1038/s41467-018-06911-w
“Pressureless glass crystallization of transparent yttrium aluminum garnet-based nanoceramics”, Nature Communications (2018) doi.org/10.1038/s41467-018-03467-7
“Accelerated Discovery of Two Crystal Structure Types in a Complex Inorganic Phase Field”, Nature (2017) doi.org/10.1038/nature22374

Work Context

The CEMHTI is a CNRS research unit spread over two nearby sites (High Temperature and Cyclotron) and employing approximately 100 people.
The laboratory develops original expertise and tools at the national and international level to study the physico-chemical properties of materials in extreme conditions.
The PhD student will be based at the high temperature site of the laboratory, will be part of the Transparent Ceramics and Structures team and will report to the team leader.

Equipment available:

The CEMHTI laboratory has excellent facilities for the synthesis and structural characterisation of glass-ceramic and ceramic materials. These include :
- Aerodynamic levitation coupled with CO2 laser heating.
- X-ray powder diffraction (in-situ measurements up to 2000°C possible).
- Scanning electron microscopy (FEG SEM coupled with EBSD)
- Ultimate resolution transmission electron microscopy.
- High temperature infrared and Raman spectroscopy.
- High field and high temperature solid state NMR spectroscopy.

Constraints and risks

Travel in France and abroad is envisaged to promote the progress of the thesis or to participate in conferences

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