Patent ID: 7247589

Claim:
Transparent polycrystalline sintered ceramic composed of Mg—Al spinel, Al oxynitride, ZrO 2 , Y 2 O 3 or Y—Al garnet, or of a mixed structure of these components, of cubic crystal structure, comprising a real in-line transmission RIT>75% of the theoretical maximum value measured on 0.8 mm-thick polished plates and for light of a wavelength between 600 and 650 nm, and wherein when the sintered ceramic is composed of Mg—Al spinel, Al oxynitride, ZrO 2 , or Y 2 O 3 , or of a mixed structure of these components, the average grain size D is in the range of 60 nm<D<10 μm, and wherein when the sintered ceramic is composed of Y—Al garnet, the average grain size D is in the range of 60 nm<D<1 μm.