against devitrification stable optical glass with high refractory index of about 1900 and relatively low dispersion of about 40 on the basis of lanthanum - tanteloxid

摘要

1299879 Glass composition PILKINGTON BROS Ltd R J PARRY and G A HIGHAM 19 Nov 1970 [9 Dec 1969] 60116/69 Heading C1M A glass composition consists essentially of, in weight per cent, SiO 2 6-9; B 2 O 3 7À5-9À5; GeO 2 1À5; Ta 2 O 5 15-20; La 2 O 3 30-50; ZrO 2 6À5-8; Gd 2 O 3 1-20 and Y 2 O 3 0-5. The glasses produced from this composition are stated to have a refractive index of the order of 1À900 and an Abbe value which increases as the lanthanum is replaced by gadolinium oxide.