Enhanced luminescence and degradation of SiO2:Ce,Tb powder phosphors prepared by a sol–gel process

Enhanced green photoluminescence and cathodoluminescence (CL) from Tb3+ ions due to co-doping with Ce3+ ions were observed from SiO2:Ce,Tb powder phosphors prepared by a sol–gel technique. Blue emission from the Ce3+ ions was completely suppressed by Tb co-doping, presumably due to energy transfer from Ce3+ to Tb3+. In addition, the green CL intensity from SiO2:Ce,Tb degraded by ∼50% when the powders were irradiated for 10 h with a 2 keV, 54 mA/cm2 beam of electrons in an ultra-high vacuum chamber containing either 1×10−8 or 1×10−7 Torr O2. Desorption of oxygen from the surface was observed during the decrease of CL intensity. The mechanisms for energy transfer from Ce3+ ions to Tb3+ ions to enhance the green luminescence, and mechanisms for desorption of oxygen from the phosphor surface that would result in decreased CL intensity are discussed.