Maîtrise des propriétés optiques de céramiques transparentes par le contrôle des paramètres physicochimiques des précurseurs et des techniques d'élaboration. Cas du YAG.

Abstract : This work aims to study the relationship between microstructure and optical properties of a Ce:YAG ceramic. The microstructural properties of a luminescent ceramic define its capacity to transmit and emit light. Considering the integrally of the elaboration process, from powder shaping to maximal densification, our goal is to identify the factors ruling the luminescence activity. Ceramics were elaborated from Baikowski’s commercial powders. The characterizations on powders particules put in evidence internal defects at the nano scale. The shaping steps (granulation, pressing and isostatic pressing) were followed by densification through hot isostatic pressing (HIP). In order to keep a thin microstructure, we did not used any sintering additives. The mastering of elaboration allowed us to fabricate ceramics with different microstructures. Some of those ceramics present good transparency. Optical characterizations confirm the influence of the investigated parameters. We note the significant impact of both quantity and dimension of secondary phases on optical properties through scattering processes. Thus, scattering affects the emission spectra of the material. A maximal luminescence yield has been observed for a submicronic grain size. Linking optical and microscopic observations, we put in evidence the influence of un-radiative absorption mechanisms on efficiency. Thanks to cathodo-luminescence scanning electron microscopy, we observed the spatial repartition of luminescence on the full range of the elaborated materials
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Etienne Lachaud. Maîtrise des propriétés optiques de céramiques transparentes par le contrôle des paramètres physicochimiques des précurseurs et des techniques d'élaboration. Cas du YAG.. Matériaux. Université de Lyon, 2019. Français. ⟨NNT : 2019LYSE1019⟩. ⟨tel-02149813⟩

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