Transparent B-Willemite Glass-Ceramics

Transparent glass-ceramics based on crystals of b-willemite solid solution can be obtained in the SiO2-Al2O3-ZnO-K2O-Na2O system. The glass-ceramics are self-nucleating via liquid-liquid phase separation and therefore require no added nucleating agents. Because they offer only tetrahedral and small intersitial sites, b-willemite crystals can serve as hosts for small, optically-active transition elements such as Cr4+. Fluorescence measurements of Cr-droped glass-ceramics based on b-willemite indicated strong Cr4+ emission over a broad range of wavelengths (1100-1700 nm).