Transparent spinel ceramics and process for their preparation

The invention relates to the field of technical ceramics and relates to transparent spinel ceramics, such as may be used for example as a protective ceramic, and methods for their preparation. The object of the present invention is to provide transparent spinel ceramics, the possible free of visible defects and having ≥ 3 mm in wavelength ranges of infrared light as measured 1000-2500 nm, an in-line transmittance of more than 82% at sample thicknesses. The object is achieved by spinel which are transparent in wavelength ranges of infrared light, consisting of sintered magnesium-aluminum spinel having an average structural grain size of ≤ 10 microns and a total maximum of 0.5 wt .-% of homogeneously distributed additions of calcium and / or strontium and / or barium which in a concentration, expressed as oxide, from 0.005 to <0.2 wt .-% CaO and / or 0.005 to ≤ 0.5 wt .-% SrO and / or 0.005 to <0 , 5 wt .-% BaO are present.