Patent ID: 7407902

Claim:
A Bismuth glass composition comprising 1.7 to 12 wt % of SiO 2 , 3 to 9 wt % of B 2 O 3 , 9.5 to 19 wt % of ZnO, 62 to 80 wt % of Bi 2 O 3 and 0.1 to 4 wt % of Al 2 O 3 , and further comprising 5 wt % or less of an oxide of Group A, 12 wt % or less of an oxide of Group B and 0.1 to 10 wt % of an oxide of Group C, wherein the oxide of Group A is at least one selected from the group consisting of Li 2 O, Na 2 O and K 2 O, the oxide of Group B is at least one selected from the group consisting of MgO, CaO, SrO and BaO, and the oxide of Group C is at least one selected from the group consisting of Sc 2 O 3 , Y 2 O 3 , La 2 O 3 , CeO 2 , Pr 2 O 3 , Nd 2 O 3 , Sm 2 O 3 , Eu 2 O 3 , Gd 2 O 3 , Tb 2 O 3 , Dy 2 O 3 , Ho 2 O 3 , Er 2 O 3 , Tm 2 O 3 , Yb 2 O 3 and Lu 2 O 3 , and the weight ratio of Al 2 O 3 to SiO 2 is 0.5 or less.