Luminescence properties and site occupations of Eu3+ ions doped in double phosphates Ca9R(PO4)(7) (R = Al, Lu)

Eu3+ doped red-emitting phosphors of double phosphates Ca9R(PO4)7 (R = Al, Lu) were synthesized by a general high temperature solid-state reaction. The phosphors were characterized by X-ray powder diffraction (XRD). The detailed luminescence properties, e. g., the emission spectra under the excitation of UV light, the photoluminescence excitation spectra and decay lifetimes were reported. The phosphors can be efficiently excited by near UV light to realize an intense red luminescence (613 nm) corresponding to the electric dipole transition D-5(0) -> F-7(2) of Eu3+ ions. The luminescence properties and the potential applications were analyzed. These phosphors were investigated by the site-selective emission spectra and the fluorescence decay curves in the D-5(0) -> F-7(0) region using a pulsed, tunable, narrowband dye laser. It is suggested that Eu3+ ions have three different crystallographic sites doped in Ca9Al(PO4)(7), and five sites in Ca9Lu(PO4)(7) host. The site assignments of Eu3+ ions in Ca9R(PO4)(7) (R = Al, Lu) were discussed on the base of both optical spectroscopy results and structural analysis.