🎉 Sortie

Mathieu Chevereau PhD defense

Elaboration of new infrared transparent ceramics by complete glass crystallization and powder sintering by Spark Plasma Sintering _**Glasses and Ceramics**_ _(_[_V&C_](https://iscr.univ-rennes.fr/glasses-and-ceramics-vc)_)_ _team_ _**Abstract**_ The work reported in this thesis manuscript focuses on the synthesis and the characterization of new infrared transparent ceramics. Gallium (III) selenide (Ga2Se3) powder was synthesized using sealed-tube method, and then sintered by Spark Plasma Sintering (SPS), to make dense and pore-free ceramics. Sintered ceramics exhibit a 100 % densification rate, and are transparent from 4,5 to 16,5 μm. However, absorption bands remain on the transmission spectra, which origins are discussed. The use of another synthesis technique (mechanosynthesis) also allowed the obtention of Ga2Se3 powder, and its sintering process is described. The sulphide glass KSb5S8 was chosen to elaborate transparent ceramics by complete crystallization of the glass. With a monoclinic structure, this crystalline phase exhibits a high birefringence. Its crystallization was therefore studied in order to determine the heat treatment conditions required to maintain a nanometer-scale grain size. KSb5S8 ceramics were obtained, but lacked transparency due to the presence of scattering centers. By slightly modifying the glass composition to KSb4,61S7,86, crystalline samples kept much of the transmission of the original glass. KSb4,61S7,86 ceramics are transparent from 4 to 13 μm, show no porosity, and are the first non-oxide transparent ceramics obtained by complete crystallization of glass. _**Jury**_ **Gaëlle DELAIZIR** - Professor - IRCER, Université de Limoges / Reviewer **Sylvain MARINEL** - Professor - CRISMAT, Université de Caen Normandie / Reviewer **Isabelle MONOT-LAFFEZ** - Professor - GREMAN, Université de Tours / Examiner **Cécile GENEVOIS** - CNRS Research engineer - CEMHTI, Université d’Orléans / Examiner **Sébastien CHENU** - Associate professor - ISCR, Université de Rennes / PhD Director **Louisiane VERGER** \- CNRS Research fellow - ISCR, Université de Rennes / PhD Co-director _**Contacts**_ [Mathieu Chevereau](https://iscr.univ-rennes.fr/mathieu-chevereau), _[mathieu.chevereau@laposte.net](mailto:mathieu.chevereau@laposte.net)_ [Sébastien Chenu](https://iscr.univ-rennes.fr/sebastien-chenu), _[sebastien.chenu@univ-rennes.fr](mailto:sebastien.chenu@univ-rennes.fr)_