Temperature dependence of narrow-band UVB photoluminescence of silica–(Gd,Pr)PO4 transparent glass-ceramic phosphors

Abstract

The effect of temperature on photoluminescence (PL) due to the 6P j → 8S7/2 (j = 5/2, 7/2) transitions of Gd3+ ions was examined between 200 and 500 K for a sol–gel-derived silica–(Gd,Pr)PO4 transparent glass-ceramic phosphor with negligible concentration quenching under excitation into the 5d–4f transition of Pr3+ ions at 220 nm. The intensity of the narrow-band ultraviolet B (UVB) PL at ∼313 nm associated with the 6P7/2 → 8S7/2 transition 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)PO4 transparent glass-ceramic window and a KrCl excimer lamp as a light source at 222 nm. The silica–(Gd,Pr)PO4 transparent 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)PO4 nanocrystals with low quenching centre concentrations in inert silica glass matrix.