Structural properties of novel energy conversion materials from synchrotron X-ray absorption and diffraction studies under extreme conditions

Start Date
22-01-2020 09:00
End Date
22-01-2020 10:00
Room 337, Central Building
Speaker's name
João Elias F. S. Rodrigues
Speaker's institute
Madrid Institute of Materials Science
Contact name
Eva Jahn
Host name
Olivier Mathon
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The present postdoctoral proposal concerns research activities to be developed at the ESRF – European Synchrotron Radiation Facility, which is located at the EPN Campus in Grenoble, France. In this proposal, we aim to investigate novel thermoelectric antimonides based on RxCo4Sb12 (R = Y, La, Ce, Yb, Er, Ho, Sr, K, Mm) skutterudites prepared under high pressure condition (typically 3.5 GPa), by X-ray absorption spectroscopy for probing the local structure. The use of high pressure is an effective tool in the synthesis of novel materials with low stability under ambient conditions or meta-stable character, leading to an increased coordination number and dense polycrystalline materials. In a second part, halide and hybrid perovskites will be investigated for optoelectronic devices in solar cells using a low-cost planetary ball milling. We will perform X-ray absorption spectroscopy investigation followed by synchrotron and neutron diffraction, in order to derive details on the structural properties and magnetic structure. These results will be compared to those obtained by Raman and reflectivity infrared spectroscopies viewing to detect local modifications in the crystal lattice. Otherwise, RxCo4Sb12 skutterudites provide unique opportunity for the fundamental investigations concerning the thermoelectricity mechanisms in compounds with high Seebeck coefficient. A study on the effect of filling elements on the magnetic and transport electric properties will be conducted through complementary techniques, including magnetic measurements (using SQUID and PPMS), DC electrical measurements, and impedance spectroscopy. Therefore, structural (by XAS and SXRD), vibrational, magnetic, and electric behavior combined with thermoelectric measurements (i.e. the Seebeck coefficient, the electrical conductivity, and the thermal conductivity) will allow evaluating the nature of the coupling between such thermoelectric quantities that define the figure of merit ZT, opening up horizons for new strategies for manufacturing high-performance thermoelectric devices. At the same time, the structural studies (by XAS and SXRD) in halide and hybrid perovskites may be an important window for probing structural or order-disorder transition mediated by octahedral tilting and delocalized process by organic species inside A-site.

In this seminar, I will briefly justify the reasons why I believe a postdoctoral at BM23/ID24 beamlines could be an unprecedented opportunity in my career since the EBS-ESRF will provide the most brilliant synchrotron light in the world. In particular, some biographic details together with my previous XAFS works, and details on the postdoctoral project will be presented covering the topic of novel energy materials studied under extreme conditions.

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