Sol–gel-derived transparent silica–(Gd,Pr)PO4 glass-ceramic narrow-band UVB phosphors

Abstract

Silica-based monolithic transparent glass-ceramics containing (Gd,Pr)PO₄ orthophosphate nanocrystals, prepared by a cosolvent-free sol–gel method, efficiently emit narrow-band ultraviolet B (UVB) photoluminescence (PL) at ∼313 nm from the ⁶P_7/2 → ⁸S_7/2 transition of Gd³⁺ ions upon excitation into the 4f–5d transition of Pr³⁺ ions. The formation of (Gd,Pr)PO₄ nanocrystals as small as ∼5–10 nm facilitates energy transfer between rare-earth (RE) ions while avoiding optical loss by Rayleigh scattering. Unlike conventional phosphors, the aggregation of Gd³⁺ ions causes no concentration quenching, and the incorporation of inert RE ions to block energy transfer, such as La³⁺ and Y³⁺ ions, is unnecessary. A glass-ceramic with a Pr³⁺ ion fraction of 0.02 exhibited the maximum internal and external PL quantum efficiencies of ∼0.98 and ∼0.91, respectively, under excitation at 220 nm.