Vacuum ultraviolet excited luminescence properties of Ca3Gd7(SiO4)5(PO4)O2:Re3+ (Re3+=Tb3+, Dy3+) phosphors

• The excitation spectra show a broad band in the region of 140–210 nm.
• Tb3+-doped sample shows strong green emission and exhibits a short decay time.
• Dy3+-activated sample exhibits white emission suitable for Hg-free lamps.

A series of Ca3Gd7(SiO4)5(PO4)O2:Re3+ (Re3+=Tb3+, Dy3+) phosphors were synthesized by a solid-state reaction, and their vacuum ultraviolet excitation and emission characteristics were measured. All the excitation spectra show a broad band in the region of 140–210 nm, which can be mainly assigned to the host absorption. For Tb3+-doped sample, the absorption bands at 230 nm and 281 nm are respectively ascribed to the f–d spin-allowed and spin-forbidden transitions of Tb3+. In Dy3+-doped sample, the f–d spin-allowed transitions of Dy3+ and O2−→Dy3+ charge transfer band have not been clearly distinguished probably because of the overlapping with the strong host absorption band. The weak bands at 267 and 288 nm are attributed to be the f–d spin-forbidden transitions of Dy3+. The concentration dependence of the emission intensity upon the excitation at 172 nm indicates that the optimal doping concentrations of Tb3+ and Dy3+ are 11 mol% and 5 mol%, respectively. The optimal Tb3+ and Dy3+-activated samples respectively exhibit yellowish green and white emitting colors due to their characteristic emissions.