Patent ID: 7592278

Claim:
A glass ceramic, having a composition consisting of (in wt.-%): SiO 2 10-50 B 2 O 3 5-40 P 2 O 5 25-75 refining agents ≦5 impurities ≦1, and 0.1-10 wt.-% of at least one constituent selected from the group consisting of M3 2 O 3 , M5 2 O 5 and M4O 2 ; wherein M3 is an element selected from the group consisting of the lanthanoids, yttrium, iron, aluminum, gallium, indium and thallium; wherein M5 is an element selected from the group consisting of vanadium, niobium and tantalum; wherein M4 is an element selected from the group consisting of titanium, zirconium, hafnium and cerium; said glass ceramic having an optical transparency of at least 50% in the range of 380 nm to 780 nm.