Fabrication of Transparent Polycrystalline ZnAl 2 O 4 – A New Optical Bulk Ceramic

There is interest in the enlarging of the bulk, transparent ceramics family. Polycrystalline ZnAl 2 O 4 may constitute a useful addition to the existent set of such materials. The objective of this work was the development of a technology allowing the fabrication of bulk, polycrystalline, transparent ZnAl 2 O 4 parts. It was determined that a nano ZnAl 2 O 4 powder, synthesized by the hydrothermal technique, can be formed into green bodies having an average pore size of 30 nm and a bulk density of ~55% TD. A two stage sintering process, in which air heating (1500°C) was followed by hot‐isostatic pressing (1550°C), densified small (20 mm in diameter) disks to a bulk density ≈TD. Such specimens exhibit an in‐line transmission of 78% (λ = 800 nm; t = 2 mm), a hardness of 10.5 GPa and an average grains size of 1.1 μm.