Preparation of highly pure, preferably radiation-stable large volume single crystals, useful in e.g. lenses, comprises producing a melt obtained from crystal raw material and controlled cooling under solidification

摘要

Preparation of highly pure, preferably radiation-stable large volume single crystals with small intrinsic birefringence comprises producing a melt obtained from crystal raw material and controlled cooling under solidification, where: fragments and/or blends of the obtained crystals is useful as crystal raw material; the crystal exhibits no color under visual observation, and on irradiating in dark room with a white light lamp exhibits e.g. (a) minimum or maximum of perceptible reddish and/or bluish fluorescence. Preparation of highly pure, preferably radiation-stable large volume single crystals with small intrinsic birefringence comprises producing a melt obtained from crystal raw material and controlled cooling under solidification, where: fragments and/or blends of the obtained crystals are useful as crystal raw material; the crystal exhibits no color under visual observation, and on irradiating in dark room with a white light lamp exhibits (a) minimum or maximum of perceptible reddish and/or bluish fluorescence, (b) minimum or maximum of perceptible diffuse dispersion, and minimum or weak discrete dispersion of maximum two visually perceptible dispersions per dm 3. An independent claim is included for a crystal for optical applications comprising a BSDF value of less than 7x10 -7, RMS homogenizes after removing of 36 Zernike-coefficients of less than 15x10 -8and a SDB RMS value in 111 direction of less than 0.2 nm/cm.