Elaboration and study of spinel-type transparent ceramics in the MgO - Al₂O₃ system

Transparent ceramics can be used in various domains (infrared windows for laser, spectrometer, controlled fusion reactor, infrared guiding, shielding, and lens for cameras operating in hostile environment like radioactive environment). As industrial applications remained limited due to difficulties of elaboration of these ceramics, this research thesis aims at studying the contributions of a recent technology: the hot isostatic pressing (HIP). This method is mainly used in post-densification where ceramics are previously degassed and pre-sintered with a closed porosity. The author justifies the choice of alumina and magnesia spinels for their physical and chemical properties, and their stability under gamma or neutron irradiation. Thus, the author describes these properties, proposes an overview of ceramic optical properties, and reports the characterization of powders. In the next parts, he reports elaboration studies (study of densification kinetics under natural sintering and hot pressing), and discusses the optical properties of products after hot isostatic pressing with respect to powder characterization, elaboration parameters and microstructure. Local defects are then studied and their origins are examined. Additional physicochemical characterizations of transparent products are finally provided