Rare Earth Doped Vitroceramics: New, Efficient, Blue and Green Emitting Materials for Infrared Up‐Conversion

New, efficient, vitroceramic hosts for rare earth luminescence are discussed. Their applications to infrared up‐conversion are emphasized. Optimized compositions lead to an efficiency nearly twice as high as commercially available . As for infrared to blue efficiency, these vitroceramics are among the best compounds obtained so far. The easy preparation in air atmosphere is described. The excitation spectra have the advantage of being broader than usual for up‐conversion phosphors. Kinetic studies present some puzzling behavior with respect to sample geometry; e.g. , the rise time increases fourfold with sample thickness between 0.1 and 4.5 mm. Segregation of rare earths in the microcrystalline phase rather than in the glassy one is clearly shown which explains the high efficiencies.