Andrea Piarristeguy

Senior Lecturer, conducting his research in the theme "Chalcogenides and Glasses" of the Department of Chemistry of Materials, Nanostructures and Materials for Energy (Department D4) of the ICGM, and teacher in the Department of Materials of Polytech Montpellier.

Scientific Manager of the thematic group "Chalcogenides and Glasses" since January 2021.

Member of the Steering Committee of GDR CHALCO (https://gdrchalco.cnrs.fr/) since January 2022.

Member of the Union for Science and Technology (USTV) (https://www.ustverre.fr/)

I. By the way

Courses & Training
Teachings & Responsibilities
Career & Training

• HDR Chemical Sciences, University of Montpellier. "Chalcogenides for Information Storage and Energy Conversion", defended on June 23, 2016.
• PhD in Materials Sciences, University of Buenos Aires (Argentina), LSA (Laboratory of Amorphous Solids). "Chalcogenide glasses: Application to battery manufacturing", defended on September 14, 2005.
• Bachelor's degree in Physical Sciences (equivalent to 1 Master's level in France), Faculty of Exact and Natural Sciences of the University of Buenos Aires (Argentina): "Structural studies of the amorphous ternary system Ge-Se-Ag by X-ray diffraction" in 2000.

Teachings & Responsibilities

Teaching:
* Department of Materials (MAT) (https://www.polytech.umontpellier.fr/formation/cycle-ingenieur/materiaux) – Support of physics (MAT3), Solid State Physics (MAT3), Glasses (MAT4), Energy (MAT4) and Materials for detection and storage (MAT5)
* Department of Mechanics and Interactions (MI) (https://www.polytech.umontpellier.fr/formation/cycle-ingenieur/mecanique-et-interactions)

– Physico-chemical properties of the subject (MI3)
* Department of Mechanics and Industrial Structures (MSI) (https://www.polytech.umontpellier.fr/formation/cycle-ingenieur/mecanique-structures-industrielles)– Physics (MSI3)
* PeiP (Polytech engineering schools) (https://www.polytech-reseau.org/cycle-preparatoire-peip/)

– Materials discovery TP

Responsibilities and animations in teaching :
* Pedagogical manager of the^4th year of the Materials Department, since 2016.
* Responsible for relations with students of the^1st cycle (Recruitment Unit), since 2010.

Collective responsibilities:
* Elected member of the Polytech Montpellier School Council, since 2022.
* Elected member of the Pool of Experts in Section 33 of the University of Montpellier, since 2017.

* Elected titular member of the ICGM Unit Council, from 2015 to 2020.

Ii. Research activities

Aging of amorphous layers Ge-Te

(a) Drift coefficients measured at 50°C over 24h and (b) Fraction of total homopolar bonds obtained by numerical simulations Reverse Monte Carlo (RMC). The insert shows the contribution of Ge-Ge (blue) and Te-Te (green) bonds for GexTe amorphous films (100-x).

Research topics
Collaborations & Contracts
Research topics

Chalcogenides and Ionic of the Solid

In recent years part of the work in the field of Solid State Ionics has concerned the study of chalcogenide glasses conducted by Ag+ used in the development of electrical memories of the CB-RAM type. The main objective was to study the consequence of phase separations on the electrical properties of glasses. The use of electrostatic force microscopy (EFM) has made it possible to characterize the percolation phenomena responsible for conductivity jumps of several orders of magnitude in the materials studied. More generally, the use of electric field microscopy (EFM, C-AFM, PF-QNM) has made it possible to characterize the local scale of each of the phases present in the glass.

More recently, we have been interested in the development of all-solid-state batteries for electrochemical energy storage. This issue is very topical. Indeed, the need to promote a future where renewable energies free of_CO2 emissions will be valued, requires the development of new electrochemical energy storage systems, whether for electric propulsion or for the storage of energy produced by intermittent sources (wind turbines, photovoltaic cells or thermal sources of solar energy). The success of lithium batteries is undeniable, but they have two limitations: they are based on the use of i) flammable liquid electrolytes and ii) lithium, a relatively expensive material with relatively low natural reserves in Europe and the USA. In some cases (stationary storage for example), it may be interesting to develop alternative solutions. For example, we can i) replace lithium with sodium and ii) develop "all-solid-state" batteries.

The development of all-solid-state batteries faces the difficulty of obtaining robust electrode/electrolyte interfaces that do not deteriorate too quickly during charge/discharge cycles. To try to limit this problem, we can propose the development of all-solid state batteries comprising glasses or glass-ceramics both as electrolyte material and electrode materials. These materials can absorb compositional changes without significant volume changes. In addition, we can consider the use of the same network formator for the electrodes and the electrolyte which can promote a better delocalization of the interfaces and the obtaining of a perfectly compacted monolithic object. The second problem that hinders the development of all-solid devices is the low conductivity of solid electrolytes in general. Among the promising solid electrolytes, chalcogenide glasses and glass-ceramics occupy a privileged place. In general, their conductivity is much higher than that of their oxide counterparts. Research has shown that partial recrystallization of glasses with precipitation of crystallites of well-controlled composition could be a way to achieve ionic conductivities of ^{10-3 Scm-1} at room temperature, a value very close to those of liquid electrolytes.

First, we are interested in identifying new electrolytes, the richest possible in sodium, including metastable phases. The most promising materials will be used by the manufacture of an "all solid" battery composed of a monolithic structure with the electrodes.

Chalcogenides for Information Storage

Intrinsically metastable, telluride glasses undergo a rapid and reversible amorphous/crystallized phase change when subjected to the action of a laser pulse or an electric pulse. The use of this effect was at the origin of the huge market for rewritable optical discs (DVDs-digital versatile disks) in the early 2000s. Now, these materials are attracting great interest, less for optical storage than for electrical storage of information.These materials are indeed used for the realization of electrical memories. Improving the performance of these devices requires the removal of a number of technological barriers, in particular that of their thermal stability and aging. For this, a better knowledge of the structure of materials in their crystalline and amorphous forms is essential. This is where our activities on chalcogenides for information storage are located, activities that began about ten years ago. They rely on our ability to produce vitreous/amorphous chalcogenides by various routes (hyperquenching, thermal co-evaporation …). We are thus able to produce materials that are very difficult to obtain in amorphous form and this, in sufficient quantities to be able to study them, among other things, by neutron diffraction. The coupled use of neutron diffraction and numerical simulation (ab initio, FPMD, Reverse Monte Carlo), carried out in collaboration with physicist colleagues (M. Micoulaut (Sorbonne University, Paris), P. Jovari (Wigner Research Centre for Physics, Budapest, Hungary), A. Bouzid (IRCER, Limoges)) allows us to access crucial information on the structure of phase change materials (demonstration of homopolar bonds, Ge environment).

Collaborations & Contracts

Current collaborations

– Laboratory of Theoretical Physics of Liquids of Condensed Matter (LPTMC) – Sorbonne University, Paris: M. Micoulaut.

– Institut Laue Langevin (ILL), Grenoble: G.J. Cuello, V. Nassif, V. Cristiglio.

– Central Technology in Micro and Nanoelectronics (CTM), University of Montpellier, Montpellier: M. Ramonda.

– Ceramic Process Sciences and Surface Treatment (SPCTS), Limoges: G. Delaizir, A. Bouzid, O. Man

– Charles Coulomb Laboratory, University of Montpellier, Montpellier: R. The Park.

– Laboratory of Reactivity and Chemistry of Solids (LRCS), Amiens: V. Viallet, V. Seznec.

– Institut Lumière Matière (ILM), Lyon: B. Ruta

– Physikalische Institut, RWTH Aachen University, Aachen, Germany: M. Wuttig, J. Luckas.

– Wigner Research Centre for Physics, Institute for Solid State Physics, Budapest, Hungary: P. Jóvári.

Contracts since 2011:

• MITI CNRS 2021 project In situ instrumentation in extreme conditions: Polyglass "A dynamical view at polyamorphism in glasses" (project leader B. Ruta, ILM)
• MITI CNRS 2020 project In situ instrumentation in extreme conditions: Polyglass "A dynamical view at polyamorphism in glasses" (project leader B. Ruta, ILM)
• SATT AxLR pre-maturation project "Electrolytes and sodium solid battery" (project leader: A. Piarristeguy). (2019-2021)
• Structuring project of the University of Montpellier "Support for research 2020": "Development of innovative materials by spark plasma sintering pressing" (Project leader: A. Piarristeguy)
• ANR Progelec VTG project: "Chalcogenide glasses and glass-ceramics as thermoelectric materials for applications around the environment" (Project leader: B. Lenoir). (2011-2016)
• ANR white TEAM project: " New functionalities of amorphous materials based on tellurium" (Project leader: M. Micoulaut). (2012-2015)
• Bilateral collaborations France-Germany (Procope DAAD-MAEE program): " Thermal stability and rigidity in amorphous phase change materials" (Project leader: V. Coulet) (2012)

Iii. Scientific production