Luminescence properties of Ca10K(PO4)7:RE3+ (RE = Ce, Tb, Dy, Tm and Sm) under vacuum ultraviolet excitation

A series of RE3+ (RE = Ce, Tb, Dy, Tm and Sm) activated Ca10K(PO4)7 were synthesized by conventional state reaction and their photoluminescence properties under vacuum ultraviolet excitation were investigated. The PO43− absorption lies within the range from 125 to 180 nm in all the excitation spectra of Ca10K(PO4)7:RE3+. The first f–d transition of Ce3+ is observed at 316 nm, and the Ce3+ emission is located at about 350 nm. Both the first spin-allowed and spin-forbidden f–d transitions of Tb3+ are situated at 232 and 263 nm, respectively. The emission spectrum of Ca10K(PO4)7:Tb3+ exhibits typical Tb3+ emissions with the predominant peak at 544 nm. The O2−–Dy3+ charge transition band was calculated and identified around 173 nm, the CIE chromaticity coordinates of Dy3+ were calculated to be 0.364 and 0.392. The Ca10K(PO4)7:Tm3+ demonstrates the strongest excitation at about 182 nm assigned to O2−–Tm3+, and gives the predominant emission at 453 nm. The 4G5/2–6H7/2 transition of Sm3+ at 601 nm is the most intensive in the emission spectrum.

Research highlights
► The Ce3+, Tm3+, Dy3+, Tb3+, and Sm3+ doped Ca10K(PO4)7 exhibit multicolor emissions.
► The Ca10K(PO4)7:Tb3+ shows a shorter decay time than the commercial Zn2SiO4:Mn2+.
► The Ca10K(PO4)7:RE enrich the luminescence materials for PDPs and Hg-free lamps.