Cathodoluminescence and photoluminescence in the core region of Bi12GeO20 and Bi12SiO20 crystals

Cathodoluminescence and photoluminescence of Bi12SiO20 and Bi12GeO20 samples are studied. Both kinds of samples show a dark orange central part or core. Emissions in the blue, green, and red spectral regions are observed. The 640 nm band is the predominant feature in the core emission. The evolution of this band during electron irradiation suggests possible emission mechanisms. In addition, two infrared emissions at about 915 and 1390 nm are detected.