Temperature dependence of narrow-band UVB photoluminescence of silica-(Gd,Pr)POtransparent glass-ceramic phosphors.

The effect of temperature on photoluminescence (PL) due to theP→S(= 5/2, 7/2) transitions of Gdions was examined between 200 and 500 K for a sol-gel-derived silica-(Gd,Pr)POtransparent glass-ceramic phosphor with negligible concentration quenching under excitation into the 5d-4f transition of Prions at 220 nm. The intensity of the narrow-band ultraviolet B (UVB) PL at ∼313 nm associated with theP→Stransition slightly increased between 200 and 300 K, but was decreased to ∼86% and ∼62% of that at 300 K when temperature was raised to 400 and 500 K, respectively. The observed magnitude of the thermal quenching of the UVB PL intensity was agreed well with that recorded in a prototype narrow-band UVB lamp consisting of another silica-(Gd,Pr)POtransparent glass-ceramic window and a KrCl excimer lamp as a light source at 222 nm.

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

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 6P7/2 → 8S7/2 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.