Luminescence and energy transfer properties of Ca8Gd2(PO4)6O2:A (A = Ce3+/Eu2+/Tb3+/Dy3+/Mn2+) phosphors

Abstract

A series of Ca8Gd2(PO4)6O2, (CGPO):A (A = Ce3+, Eu2+, Tb3+, Dy3+, Mn2+, and their combination), phosphors with the oxyapatite structure have been prepared via a Pechini-type sol–gel process. X-ray diffraction (XRD), photoluminescence (PL) spectra, cathodoluminescence (CL) spectra, absolute quantum yield and lifetimes were utilized to characterize the samples. Under UV and low voltage electron beam excitation, the Ce3+ ion, as a sensitizer, can transfer its energy to other activators (Eu2+, Tb3+, Dy3+, and Mn2+) in the CGPO:Ce3+, Eu2+/Tb3+/Dy3+/Mn2+ system. The energy transfer from Ce3+ to Eu2+ and Tb3+ has been demonstrated to be a resonant type, via a dipole–dipole and dipole–quadrupole mechanism, respectively, and the critical distances are calculated to be 28.70 and 12.60 A, respectively. The absolute quantum yields of the Ce3+ and Eu2+ coactivated CGPO phosphors are enhanced with respect to those of the Eu2+ singly activated samples via energy transfer. Under the excitation of a low voltage electron beam, the emitting colors of CGPO:Ce3+/Tb3+/Dy3+/Mn2+ samples can be adjusted from blue to green, and from blue to white to yellow-green by control of the contents of Ce3+, Tb3+, Dy3+, and Mn2+. The CL properties have been investigated in detail, and the results indicate that the as-prepared Ca8Gd2(PO4)6O2:A (A = Ce3+/Eu2+/Tb3+/Dy3+/Mn2+) samples have good CL intensity and CIE coordinate stability with a wide color-tunable emission. Based on the good PL and CL properties and the varied hues of the CGPO host by adjusting the concentration of the activators (Ce3+/Eu2+/Tb3+/Dy3+/Mn2+), CGPO might be promising as a host material for use in solid-state lighting and display fields.