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. The silica-(Gd,Pr)POtransparent glass-ceramics was more resistant to the thermal quenching of the narrow-band UVB PL than a conventional powder phosphor, probably because of the encapsulation of (Gd,Pr)POnanocrystals with low quenching centre concentrations in inert silica glass matrix.