Novel Dy3+-doped Ca2Gd8(SiO4)6O2 white light phosphors for Hg-free lamps application

The luminescent properties of Ca2Gd8(1−x)(SiO4)6O2:xDy3+ (1% ≤ x ≤ 5%) powder crystals with oxyapatite structure were investigated under vacuum ultraviolet excitation. In the excitation spectrum, the peaks at 166 nm and 191 nm of the vacuum ultraviolet region can be assigned to the O2− → Gd3+, and O2− → Dy3+ charge transfer band respectively, which is consistent with the theoretical calculated value using Jφrgensenʹs empirical formula. While the peaks at 183 nm and 289 nm are attributed to the f–d spin-allowed transitions and the f–d spin-forbidden transitions of Dy3+ in the host lattice with Dorenbosʹs expression. According to the emission spectra, all the samples exhibited excellent white emission under 172 nm excitation and the best calculated chromaticity coordinate was 0.335, 0.338, which indicates that the Ca2Gd8(SiO4)6O2:Dy3+ phosphor could be considered as a potential candidate for Hg-free lamps application.