Correlation between MgAl2O4-spinel structure, processing factors and functional properties of transparent parts (progress review)

Efforts were and are made to develop performant fabrication technologies, for transparent polycrystalline spinel – a material used for armor, infrared windows and other products. Significant progress was made – during some fifty years of research – regarding the understanding of the structure of spinel, at various scales, and the best ways to correlate processing with the relevant structural features so as to improve properties. This review compiles and comments the results of this progress, using as sources the literature and the authorʹs own work. As of now the best specimens obtained combine submicron grains with an optical transmission close to the theoretical and a Vickers hardness of 15 GPa (size ≤25 cm). Larger plates, more than 0.5 m in size, but with coarse microstructure and lower hardness, have also been produced, together with quite large dome shaped parts, exhibiting highly uniform optical properties.