Blue-green luminescence properties and charge compensation of Ca9MgLi(PO4)7 doped with Tb3+ and alkali metal ions

Ca9MgLi(PO4)(7): 4%Tb3+, 4%R+ (R = Li, Na, K) phosphors were synthesized by a solid-state reaction method. The crystal structure, morphology, composition and luminescent properties of as-prepared samples were characterized by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), energy dispersive spectrometer (EDS), high-angle annular dark field (HAADF) and spectroscopy technique. The effect of a small concentration of charge compensators like Li+, Na+, K+ on Ca9MgLi(PO4)(7): Tb3+ phosphor has also investigated. Ca9MgLi(PO4)(7): Tb3+, R+ (R = Li, Na, K) exhibit superior blue-green luminescence around D-5(4) -> F-7(5) (543 nm) to Ca9MgLi(PO4)(7): Tb3+ and can be effectively excited by 370 nm light, which implies that efficient charge compensation can promote the emitting of Tb3+ in Ca9MgLi(PO4)(7). The CIE coordinates and decay lifetimes of typical samples were also studied. The Ca9MgLi(PO4)(7): Tb3+, R+ (R = Li, Na, K) have promising application as a blue-green phosphor for near-ultraviolet chip excited white LEDs.