Highly transparent, bright green, sol–gel-derived monolithic silica-(Tb,Ce)PO4 glass-ceramic phosphors

Abstract

Monolithic silica glasses containing TbPO₄ nanocrystals with narrow size distribution and exhibiting excellent ultraviolet (UV) transparency have been prepared using a cosolvent-free sol–gel method. Despite the high refractive index of TbPO₄ crystals (∼1.8), observed Rayleigh scattering from the crystals is negligible because of the small average crystal size (∼5 nm). The precipitated crystals are of the metastable monoclinic form, different from the stable tetragonal form. The glasses are UV photoluminescent, even at stoichiometric Tb composition, and doping with a small amount of Ce³⁺ ions increased the external quantum efficiency to ∼0.76 under excitation at 290 nm. Unlike conventional glassy phosphors, the photoluminescence efficiency is high despite the high SiOH concentration of the glass matrix because of confinement of RE ions to the crystal phase.