Missions

Synthesis in solution can provide HP samples which, depending on the implementation, present a variety of defect contents. Mild crystallization conditions in bulk solutions leads to crystals with very low defect contents (strain, dislocations…). As such, it will be used to produce reference samples. Alternatively, by adapting systems already in place at Institut Néel, crystallization in solution further away from equilibrium should lead to powders with increasing amounts of defects. These samples of varying defect content compared with those derived from mechanosynthesis, will enable to study the contribution of the defect structure, aiding in identifying which defect types that are beneficial to EMWA.

Activities

- Synthesis of hybrid perovskites and/or precursors (primary task)
- Adaptation of crystallization systems to hybrid perovskites (secondary task)
- Determination of process points for perovskite synthesis (primary task)
- Structural, spectroscopic characterizations of powders (XRD, Raman, SEM, UV-Vis, PL…) (primary task)

Skills

- Solution chemistry
- Hybrid Perovskites Chemistry
- Crystallization in solution
- Solid state characterizations

Work Context

The increased use of electronic devices and the rapid development of associated technologies (like the advent of fifth generation wire-less communication) have led to interferences issues from various systems (cell phones, wireless LANs, satellite broadcasting systems, etc) and significant electromagnetic wave pollution. To tackle these challenging issues, electromagnetic absorbing materials in the corresponding frequency domain (GHz) are urgently pursued. ElectroMagnetic Wave Absorbing Materials (EMWAMs) exhibit either magnetic or dielectric loss, the energy absorbed from the radiation being ultimately converted into heat, dissipated into the environment. In that context, the ABPERO ANR project aims at developing new EMWAMs based on hybrid perovskites (HPs). HPs are complex dielectric materials exhibiting a broad range of polarization mechanisms, which have been very little studied for this application. Because those mechanisms are strongly influenced by the structure of the HP and the defects present, both aspects will be studied. Several HP structures will be considered and for each two synthesis routes will be explored to reach various types and concentrations of defects: a chemical approach using solutions and mechanosynthesis. The obtained HP powders, will then be used to form the composite materials to be evaluated as EMWAMs. The targeted features are a high absorption over a wide range of GHz frequencies, easy shaping, low thickness and stability (chemical, thermal).

In the framework of this project, the candidate will be involved in the chemical route for the synthesis of HP powders at Institut Néel (Grenoble, France). He will join the Plum Dept in the Optics & Materials (OptiMa) team, a group of 15 physicians, theoreticians and physico-chemists. This work will be carried out with two supervisors at Institut Néel and in close collaboration with teams at ICPEES (Strasbourg, France) that will be in charge of the mechanosynthesis of HPs and at IPCMS (Strasbourg, France) for the evaluation of the EMWAMs composites.

The Institut NÉEL is a CNRS unit (UPR 2940) under agreement with the University Grenoble Alpes. The laboratory is related to the CNRS Physique. It is located in Grenoble, in the heart of a unique scientific, industrial and cultural environment. It is one of the largest French national research institutes for fundamental research in condensed matter physics enriched by interdisciplinary activities at the interfaces with chemistry, engineering and biology. It consists of 450 employees, including 175 researchers.

The position is located in a sector under the protection of scientific and technical potential (PPST), and therefore requires, in accordance with the regulations, that your arrival is authorized by the competent authority of the MESR.

Constraints and risks

Hybrid perovskite are generally lead-base compounds synthesized in organic solvents. As such the chemical risk is key and following safety protocols is paramount (for synthesis as well as handling of sample, precursors and synthesis by-products).